Another milestone they count down in Times Square, less deliriously, is the moment a company goes public by selling shares on the Nasdaq Stock Market. Thursday, May 3, at 9:29:50 a.m., it’s the turn of the Carlyle Group, Washington’s semi-mythic private-equity leviathan, the capital’s most fabled generator of cash, conspiracy theories and conspicuous philanthropy.

Ten, nine, eight . . .

David Rubenstein, the public face of Carlyle, who spends his free time and money on missions such as repairing the Washington Monument after an earthquake, rescuing the Magna Carta from the auction block for the National Archives and funding the panda research program at the National Zoo, is not counting down. He stands, owlish and impassive, in Nasdaq’s fishbowl studio, seeming slightly stricken by the clamor of a soundtrack that gallops like a techno version of “Chariots of Fire.”

The action is being beamed around the world, and a seven-story video screen on the front of the building splashes the proceedings onto the square outside. But Rubenstein and co-founders William Conway and Daniel D’Aniello stay beyond camera range. The last place Rubenstein wants to be is seven stories tall in Times Square at the moment the market certifies him, somewhat redundantly, as a billionaire.

Seven, six, five . . .

Egged on by bubbly Nasdaq producers wearing headsets, the voices counting down for the cameras belong to a half-dozen high school sophomores and executives connected with Junior Achievement, a favored charity of Carlyle’s. By shining the spotlight away from itself, it’s almost as if, at this culmination of Carlyle’s emergence from a past reputation of opaque, insider-power connections, the firm were attempting to go public as privately as possible.

Four, three, two, one . . . ding-ding-ding-ding!

The sound marks the symbolic start of trading and the symbolic opening of a new chapter for 25-year-old Carlyle — and for Rubenstein, 62, who has charted his own trajectory from obscurity to public man-for-all-causes. He has done it with a paradoxical combination of grand gestures grounded by the self-effacement and self-deprecation of someone who, in important respects, still feels compelled to work as hard as he can to amount to something.

To Rubenstein, there is always more to do — at Carlyle and away from Carlyle.

“I have always looked at things from the perspective of, how does this fit in the context of what am I doing on the face of the earth, and what am I doing to justify my presence here?” he says later. “Moneymaking was never anything to me. I was happy never making money; I just was happy doing things I liked. But I fell into the money thing. I now don’t feel guilty about it, but I am determined to give away the bulk of it and enjoy doing it.

“My biggest concern now is, I’m 62, and how many more years can I go at this pace?”

Rise of a bookish child

Nobody who knew him saw this coming — not former Baltimore mayor Kurt Schmoke and the guys from the old Baltimore neighborhoods, not Jimmy Carter and his aides in the White House, not the Wall Street pooh-bahs who disdained ex-feds as salarymen with no business sense.

Certainly not Bettie Rubenstein, the homemaker wife of Bob, a retired postal worker who never earned more than $8,000 a year. Neither had finished high school. Bettie’s simple wish for their bookish only child was that he one day become a dentist.

“No one would have anticipated that he would be where he is today,” says Stuart Eizenstat, Carter’s domestic policy adviser, whose shy, smart, hard-working 27-year-old deputy was Rubenstein. “It’s a real story about how a person can grow and develop and surprise everybody, except himself.”

CBS correspondent Rita Braver has watched Rubenstein’s rise since she was an overnight news producer in the Carter era. When news would break past midnight, she knew that Rubenstein would be the only staff member still at work in the White House, able to explain things, on background, of course.

“I’ve met lots of people who’ve gotten to be quite big,” Braver says. “They have a certain swagger about them, and they’re always trying to let you know how important they are. With David, it’s quite the opposite. He’s got no swagger. And he is sweet.”

When in Washington, Rubenstein — a teetotaling vegetarian — drives himself in his 12-year-old Mercedes station wagon. He also spends 1,100 hours a year airborne in his Gulfstream jet on Carlyle business, which, adding time on the ground, amounts to 250 travel days a year. (To help attract investors before the public stock listing, he addressed 75 meetings in two weeks on four continents.)

He met his wife, the former Alice Rogoff, when she worked at the Office of Management and Budget during the Carter administration. The two young aides competed with each other to get their memos on top of the pile in Carter’s in-box. Rogoff — who once worked as an assistant to Donald E. Graham, then-publisher and now chief executive officer of The Washington Post Co. — became chief financial officer of U.S. News & World Report. Now, she is a co-founder of the Alaska Native Arts Foundation and publisher of the online Alaska Dispatch. They live in Bethesda and have three children — two daughters who graduated from Harvard and a son at Duke, which Rubenstein attended on a scholarship.

Almost everyone loves a generous billionaire. But skeptics, including some journalists and government watchdogs, say Rubenstein owes the foundation of his wealth to his savvy recruitment of powerful Washington insiders — such as former defense secretary Frank Carlucci, former secretary of state James Baker and George H.W. Bush — to work with Carlyle in various capacities during Carlyle’s skyrocketing adolescence as a private-equity firm in the 1990s. In its business of using investors’ money and bank loans to buy and sell companies for a profit, Carlyle helped pols cash in on their public service, critics say.

Rubenstein denies that those heavyweights improperly influenced the U.S. government on behalf of Carlyle. Mainly, he says, they made it easier to raise money from investors, at a time before David Rubenstein was David Rubenstein.

Inspired by a president

On a chilly midday in January 1961, in the living room of a two-bedroom brick rowhouse in a virtually all-Jewish, blue-collar section of Baltimore, a black-and-white television showed an idealistic young president delivering a stirring speech.

. . . And so, my fellow Americans, ask not what your country can do for you; ask what you can do for your country. . .

Eleven-year-old David Rubenstein was permanently inspired. The next day, his sixth-grade teacher drove home the message by presenting the speech as a class lesson. Ever after, Kennedy’s inaugural address would play a decisive role in his life, sometimes overtly, sometimes implicitly.

Rubenstein began forming an ambition to be a lawyer and serve in the government. While at Baltimore City College high school, he joined the Lancers Club, a fabled citywide institution mentored by Baltimore judge Robert Hammerman, who died in 2004. The club convened Friday evenings for sports and guest speeches by politicians and public figures.

“I just remember him questioning some of the political leaders and having great insights into their work,” recalls Schmoke, now dean of the Howard University Law School.

Rubenstein chose Duke from among several colleges that accepted him, because Duke offered the biggest scholarship. Four years later, he picked the University of Chicago Law School for the same reason.

He landed a job in 1973 at the New York law firm that also employed former John F. Kennedy speechwriter Ted Sorensen — so he could be near the man credited with helping to draft Kennedy’s inaugural address.

“I didn’t think I had the money to be a candidate, the charm, the looks, the personality,” Rubenstein says. “I could be the adviser. And so my role model was Ted Sorensen, who had written the great speech.”

In 1975, Rubenstein became chief counsel to the Senate Judiciary Committee’s Subcommittee on Constitutional Amendments. Visiting her son on Capitol Hill one day, Bettie Rubenstein marveled at his progress. She could tell that skipping dentistry was working out.

She recalls saying to him, “ ‘I never dreamed you would be working at the Senate.’ He looked over at the White House and said, ‘Next time, I’ll be working in the White House.’ ”

Eizenstat drafted Rubenstein to work on Carter’s presidential campaign. When Carter won, Rubenstein became deputy domestic policy adviser. Newsweek published a profile of “one of Carter’s most effective aides,” the “White House Workaholic.”

“He never put himself forward,” Carter says in an interview. “He was always very reticent about taking the initiative to speak up, but when I would ask him a question, he would invariably know the answer.”

Eizenstat adds: “David certainly didn’t have charisma. There was almost a negative charisma. But what he had was a sort of intensity of intellect and dedication and devotion to public service. . . . That endeared you to him. That was its own magnetism.”

Carter’s defeat after one term and the career wilderness that staff members plunged into were jarring to Rubenstein. He was going to have to find a different way to answer Kennedy’s challenge.

“I tried to help my country, and it didn’t work,” he says. “We got thrown out. When you get 19 percent inflation, you don’t think that your country is waiting for you to come back.”

It took months to find a job with a Washington law firm, but he decided the practice of law wasn’t for him after all. He had read that entrepreneurs tend to start companies between the ages of 28 and 37. He turned 37 in 1986 and feared the window was closing. After some false starts, he decided he would co-found a buyout firm. He knew how unlikely it seemed: He had no business experience, and he wanted to open shop on Pennsylvania Avenue NW — not Wall Street.

“I thought I wasn’t going to go back in government, I didn’t have a great future as a lawyer, and I took a gamble,” he says. “Many people who start companies don’t do it for logical reasons.”

Before he made the move, while he was a lawyer working on behalf of video-recorder manufacturers in their battle with Hollywood studios, he went to Japan on business. On a Tokyo bus, he outlined his plan to Ron Brown, a lawyer and future commerce secretary, and Gary Shapiro, then chairman of the Home Recording Rights Coalition.

“Ron and I were like, ‘Right, David,’ ” Shapiro recalls. “Ron and I just laughed. We probably should have invested.”

The founding partners, including former Marriott executive Stephen Norris, raised $5 million from investors including T. Rowe Price, Alex. Brown & Sons and the Richard K. Mellon family. They selected a name inspired by a fancy hotel in New York, because it suggested an air of old-world class and because one of Norris’s heroes, financier Andre Meyer, had lived in the hotel.

The Carlyle Group was formed in 1987, as Rubenstein turned 38.

Carving out a role

One Saturday early in the young firm’s life, Norris stopped by the office with a colleague to find Rubenstein at his desk, hard at work on a memo. They suggested he take a break, get some exercise.

Rubenstein, Norris recalls, looked up and said, “Think of this as me playing golf.”

The lapsed lawyer knew he had to carve out a role that would make him useful alongside his partners, who boasted successful careers at Marriott and MCI.

“I realized that I didn’t have the financial skills that the other guys had,” Rubenstein recalls. “I thought one of the useful things I could do would be to help raise money [to invest in companies]. So I made myself into a salesman, in effect, and a fundraiser.”

For the shy former policy wonk, “that was not natural, but I learned how to do it.”

He did it his way. He was not a backslapper, a let’s-play-golfer. He hit the road, making understated, fact-packed pitches, and, in the process, becoming the front man he had never been.

Ed Mathias, an executive at T. Rowe Price who advised the partners before joining Carlyle, says: “David transformed himself, but I would put it under the guise of, he did what was necessary. . . . He’s extremely competitive and extraordinarily capable, so he adapted. I don’t know that he changed his personality, but he certainly developed the skills that enabled him to be successful.”

The early years were a struggle. “We were basically focused initially on survival,” says Norris, who would leave after several years to start his own firm.

Carlyle began to find its groove after the partners recruited Carlucci as vice chairman in 1989 (later, he became chairman) to raise the firm’s profile and help spot investment opportunities. Carlyle started buying and selling defense and aerospace contractors, including Magnavox, an electronics manufacturer (profit: $270 million); BDM, an information services firm (profit: $310 million); and Howmet, a jet engine parts manufacturer (profit: $680 million).

Investments were made through vehicles called buyout funds — pools of cash that Rubenstein raised from major investors, including wealthy individuals, pension funds and corporate endowments. Carlyle’s piece of the action was the industry standard 20 percent of the profits on the funds. Rubenstein’s fortune started accruing from his share of the 20 percent, plus the gains on his personal investments in the buyout funds.

The other 80 percent of the profits went to the investors whom Rubenstein had courted. Rubenstein also assumed the role of strategist and mapper of new frontiers that Carlyle should cross. He pioneered the idea of creating multiple funds focused on different industries, geographies and types of investment. He was one of the first to globalize private equity; Carlyle would ultimately have offices on six continents.

As Rubenstein innovated, Conway and D’Aniello oversaw investments and ran operations, respectively. The unique chemistry among the three partners proved as long-lasting as it was rare in American business: There was no chief executive and never a raised voice. It was management by consensus — and by staying out of each other’s way.

“Largely what Carlyle is today is the vision David had, even before Bill and me,” D’Aniello says.

Another of Rubenstein’s bright ideas was to associate Carlyle with former statesmen. Baker became a partner. Former president George H.W. Bush became a senior adviser. Former British prime minister John Major, for a time, headed Carlyle’s European operation. Former Philippines president Fidel V. Ramos and former prime ministers of Thailand and South Korea became advisers.

“Nobody ever heard of Rubenstein in those days,” Rubenstein says. “So if you get invited to a lunch and Rubenstein is going to speak, you’re not going to show up. But if Baker is going to speak, you would go.”

After a speech in which Bush or Baker would discuss world affairs — and, by the way, say something nice about Carlyle without touting specific deals — Rubenstein would move in with specifics on where the luncheon guests could park their millions. (The firm declines to disclose how much former officials earned from Carlyle.)

“David is an inordinately hard worker, and totally trustworthy,” Bush says by e-mail. “It doesn’t hurt that he also has a great grasp of world affairs and how that intersects with business.”

A 1993 article in the New Republic by Michael Lewis and a 2003 book by Dan Briody accused Carlyle of becoming a cash machine for these ex-officials to mon­etize their political connections. Government watchdogs charged that public policy was being swayed to benefit investors.

“This was good old-fashioned cashing in,” says Charles Lewis, founder of the Center for Public Integrity and now a professor of journalism at American University.

Rubenstein says, “Nobody can ever cite one example” of public policy being improperly tailored to suit Carlyle’s bottom line.

Suspicions mounted after the Sept. 11, 2001, terrorist attacks, when it emerged that on that day, Carlyle was hosting a business conference at the Ritz-Carlton in Washington with guests including a member of the bin Laden family. Bush addressed the conference the day before. Carlyle ended up returning the bin Laden family’s $2 million investment. The event was fodder for a sharp, mocking scene in Michael Moore’s documentary “Fahrenheit 9/11.”

Rubenstein said he understood that the growing impression of Carlyle as an unaccountable power player threatened its reputation.

“I fault myself for letting our image get tarnished,” he says. “We ended the relationships” with former statesmen.

He set Carlyle on a course that the firm’s newly hired public relations specialist, Christopher Ullman, called “glasnost” at the time, or opening up to increased public scrutiny via a Web site, annual reports and answering reporters’ questions. Louis Gerstner, a former top executive at IBM, succeeded Carlucci as chairman and instead of ex-politicians, the company’s advisory board was filled with business people.

And so, in time, from a seed of $5 million and 10 employees, Carlyle grew to $147 billion in assets under management, with more than 1,300 employees and another 650,000 working for the 200-plus companies it owns. In 25 years, it has returned $68 billion to investors. Defense companies are now a small part of the portfolio, which ranges from Dunkin’ Donuts and Hertz to Brazil’s largest lingerie manufacturer, real estate in London, natural gas pipelines in the United States, forests in China and highway service areas in Connecticut.

On the Nasdaq, Carlyle stock closed Monday at $21.06, below its initial listing price of $22 a share.

In 2006, Bush introduced former congressman Michael Huffington to Rubenstein at a dinner in Iceland to honor the former president. They talked about investment possibilities for Huffington, and months later, after more conversation and a letter from Rubenstein, Huffington invested $20 million, according to a 2009 lawsuit Huffington filed, accusing Rubenstein and Carlyle of deceptive practices, after he lost the whole $20 million.

The money had gone into Carlyle Capital, a unit that invested in high-grade mortgage-backed securities. Rubenstein had told Huffington that “the downside is very limited,” according to the complaint. But with the onset of the recession and the mortgage crisis tied to riskier securities, the value of Carlyle Capital’s assets declined, and bank lenders pulled their support. The collapse of Carlyle Capital in 2008 was Carlyle’s biggest setback, costing investors $600 million.

Rubenstein declined to comment on pending litigation. Carlyle lawyers have said Huffington received ample disclosure of the risks. A federal court in Massachusetts dismissed the complaint. A state court judge in Delaware ruled last month that the case could proceed in that state.

The Carlyle Capital debacle is the exception. Most Carlyle investments have turned out exceedingly well, with buyout and growth funds producing an 18 percent annual return to investors. Its best deal ever, China Pacific Life, a Shanghai insurance company, has produced a gain of several billion dollars in the past few years, with more to come, as Carlyle holds on to its stake.

Still, the question lingers: How does a spectacular mid-career leap into private equity apply to Kennedy’s challenge to serve your country?

“It’s clear to me when you do private equity well, you’re making companies more efficient and helping them grow and become more profitable,” Rubenstein says. “That success means our investors — such as public pension funds — benefit, which contributes to the economic wealth of society.”

Becoming D.C.’s Mr. Fix-it

Earlier this year, Rubenstein stood before a scrum of reporters and cameras in the conservation lab of the National Archives. Beside him was a new, space-age case constructed from a 300-pound block of aircraft aluminum, majestically displaying the Magna Carta, just restored and sealed in argon gas.

For years, in a more faded state and an old case, the document had been on view at archives, until the previous owner, Ross Perot, put it up for auction in New York. Rubenstein showed up on the spur of the moment and bought it for $21.3 million. Sotheby’s officials had to ask who he was. Rubenstein loaned it permanently to the Archives. He gave $800,000 for conservation and the new case and $13.5 million for a new exhibit area.

One of the reporters in the scrum looked away from the billionaire and toward the assembled archivists and experts and said, “Could someone please give us a Magna Carta 101?”

“Yes, I can do it,” Rubenstein replied — and he casually launched into a detailed disquisition on English feudal politics, kings, popes, common law, wax seals and the march of human rights from the years 1215 and 1297 to 1776, 1787 and 1791.

The performance was vintage Rubenstein — late Rubenstein, a man in whom the various strands of his life appear to be coming together in a satisfying way.

The charisma-challenged White House wonk has become a speechmaker much in demand, from the economic forums of Davos, Switzerland, to Washington think tanks, corporate retreats and college campuses — droll, deadpan, fact-filled.

Last year at the Kennedy Center, Rubenstein adroitly hosted a large and solemn gathering of the diplomatic and political tribes of Washington, including President Obama and former president Bill Clinton, at a memorial service for the go-to special envoy Richard Holbrooke.

“He set the tone of it in a way that was clearly thought out but came across as being conversational and casual, so it felt more intimate,” says Strobe Talbott, president of the Brookings Institution, where Rubenstein is a vice chairman.

On stage at the Aspen Institute Ideas Festival last year, Rubenstein spent an entertaining hour comparing and contrasting what he said were the two greatest presidential speeches: the Kennedy inaugural (“I was inspired by it”) and Abraham Lincoln’s Gettysburg Address (which he memorized in the fifth grade).

At the same time, he has become Washington’s Mr. Fix-it.

Philanthropy may be one way a rich man can answer Kennedy’s “ask what” question. Rubenstein started his streak of serious giving in 2002 — the same year he course-corrected Carlyle’s image toward more openness — with a $5 million gift toward the completion of a public policy building at Duke. It was also around then that he realized, actuarily speaking, that he had lived about two-thirds of his life. He decided it was time to get busy as a philanthropist.

“You can only do three things with your money,” he says. “You can spend it. You can invest it. Or you can give it away. And if you invest it, you’re really just getting more money to give away or buy something. How many things can you buy? So I don’t really think there’s a lot of choices.”

He has given a total of $44 million to Duke, his largest single beneficiary to date, followed by Harvard ($30.5 million) and the Kennedy Center, where he is chairman and has given $25 million — the center’s largest donor ever.

Other big gifts: $17 million to Lincoln Center; $10 million to the University of Chicago Law School; $10 million to the White House Historical Association; $7.5 million for the Washington Monument; $6 million to Johns Hopkins; $5 million to the Library of Congress National Book Festival; $4.5 million for the National Zoo’s panda research program.

Along the way, Rubenstein has developed a side specialty in buying essential national documents and loaning them back to the nation or educational institutions — including the Emancipation Proclamation in the Oval Office, a rare copy of the Declaration of Independence at the State Department, a copy of the 13th Amendment recently exhibited at the New York Historical Society, and the first map of the new nation at the Library of Congress.

He declines to disclose the extent of his giving, but tallying published reports yields a total of at least $200 million in the past 10 years.

His big gifts to marquee institutions frequently aim to expand access and opportunity to young people in need of the same monetary and mentoring boosts that set him on course. At the Kennedy Center, he supports programs to engage a younger and more diverse audience. At Harvard, he provides scholarships for those who could not afford to study for careers combining business with public service.

Not so well-known are the small gifts to local students and teachers. At the Everybody Wins! literacy program gala in March, he surprised supporters when, without notice, he whipped out a check for $50,000. He gives $110,000 worth of scholarships to 10 winners of an annual Junior Achievement essay contest that draws 1,600 submissions. He gave $205,000 last year to reward excellent teachers and principals in the D.C. public schools.

That gift started at $70,000 in 2010. “He says to me, ‘Why are we only giving this to seven teachers?’ ” recalls Kaya Henderson, chancellor of the D.C. schools. “I said, ‘Because you only gave us $70,000.’ He said, ‘If I give you more money, could you do more teachers?’ Literally I burst into tears. I was like, ‘Yes we can!’ ”

Philanthropy has put Rubenstein in the news as never before. Is it vainglory? “Some people say that the best philanthropy is done anonymously,” he says. “I’m not saying that’s not right. Other people would say that by being public about it, you encourage other people. I guess that’s the path I’ve chosen.”

Now that Carlyle is public, Rubenstein’s pace at the firm continues to be driven, while the demands of philanthropy expand. He is simultaneously leading capital campaigns at Duke, the Smithsonian and Harvard’s Kennedy School.

Meanwhile, he stays in touch with his old Lancers buddies and hosted a Lancers reunion last summer at his house in Nantucket, Mass.

And the speech invitations, the honors and huzzahs keep rolling in. Almost everybody loves a generous billionaire. Rubenstein seems believably humble, if only because in every speech he paints himself, half-seriously, as something of a disappointment.

Most recently, the Consumer Electronics Association, his old comrades from the video-recorder wars, saluted him with a Digital Patriot award at a gala in the Newseum.

“I looked up the word patriot and said, ‘Wow, I’m a patriot now,’ ” Rubenstein told the gathering. “But I’m really not a patriot. A real patriot is somebody who works for the government of the United States, or any other government, teaching children, doing work as a fireman, working as a policeman, doing the kind of work where you don’t make the kind of money I’m fortunate to make, but doing it because they’re trying to make the world a better place.

“I’m proud to take this award, but I do it in the shadow of people that I think are truly patriots.”

CEA chief Shapiro, who once laughed at Rubenstein’s vision, responded: “For an underachiever, you’ve come a long way.”