Marvin McIntyre is a nationally acclaimed financial adviser. (Sarah L. Voisin/The Washington Post)

The Three Billion Dollar Man has something to say.

Always has.

When Marvin H. McIntyre III came back from Vietnam, tooling around in a convertible Corvette he won in a poker game, he tried to say it in song. He drove down to Nashville to become a star. 

The radio DJs played ­anti-establishment anthems, screeds against the war, songs about love-ins and peace-ins and hippie picnics. But McIntyre was having none of that. He penned patriotic melodies, with titles such as “In the Face of a Child” and “A Soldier’s Story.” And he flopped.

Marvin McIntyre’s book, “Inside Out,” is a political thriller. (Sarah L. Voisin/The Washington Post)

The Corvette is long gone. It has been replaced by the sleek car-service sedans that collect McIntyre each weekday morning at his Potomac home and squire him to his downtown Washington brokerage office. There, he invests $3 billion for an astounding array of wealthy clients that has included best-selling authors and nearly 100 professional athletes, such as basketball stars Michael Jordan, Patrick Ewing and Joakim Noah, and tennis legends Arthur Ashe and Stan Smith.

McIntyre’s friend and client Kitty Kelley, the celebrity biographer, calls him “Wizard.” Business types have called him the “Broker King.”

Yet in the back seat of those comfy sedans, a convenience that he’s enjoyed for the past three decades but is bashful about discussing, he’s still working through those same creative urges that drove him to Nashville. Scribbling in longhand on legal pads, he conjures thrillers set in the darker recesses of the financial and regulatory worlds, the latest of which, a page turner called “Inside Out,” came out in late January.

McIntyre embodies a kind of Washington archetype. In a town preternaturally attuned to the men and women who occupy a single building on Capitol Hill and another on Pennsylvania Avenue, he represents a sort of durable power impervious to the vagaries of election cycles. Inside all those shapeless downtown office buildings are masters of various universes, business powerhouses who make millions of dollars, discreetly control industries and move markets but hardly draw any notice.

“You can be a rock star in this industry and be unknown here except to your family and friends,” McIntyre says one afternoon in the conference room of his tastefully appointed suite of Pennsylvania Avenue offices, a short walk from the White House.

McIntyre, a ruddy 69-year-old with an informal manner and a master pitchman’s quick, rascally wit, springs from a family with Washington bona fides to spare. His grandfather Marvin H. McIntyre, a onetime newspaperman who did a stint as The Washington Post’s city editor in the early 1900s, served as Franklin D. Roosevelt’s personal secretary. The Navy named a World War II attack transport ship after him. McIntyre’s father, later an IBM executive, used to splash around in the White House pool.

As a young man, McIntyre thought it might be fun to go by his middle name, Hunter, but opted for his stodgier full name because he thought it would stand out more. He followed his father’s footsteps to the Citadel, a “brutal” place he despised but has come to appreciate now as a member of its business school advisory board. He became a first lieutenant in the 1st Infantry Division and ran night patrols in Vietnam, but he figures he never managed to hit anyone with the shots he fired. “My main goal was to hide,” he cracks.

After his return from Southeast Asia and his dalliance with music, a friend steered him to the financial world by posing a simple question: “You can BS?” 

“Yeah, I can BS,” he responded.

Decades later, he’s fond of saying he has a PhD in BS. He can get away with a wisecrack (or a dozen) because he brings in the megabucks, routinely placing in the upper echelon of the Barron’s list of the nation’s biggest brokers. He is such a behemoth that a few years back his blessing was widely considered a key indicator of whether the corporate marriage of Legg Mason, where he was the star broker, and Citigroup would go through. In a now legendary dinner before the deal at Shula’s in Baltimore, Charlie Johnston, the head of Citigroup’s Smith Barney brokerage division, planted himself next to McIntyre all night.

“Charlie Johnston sure wasn’t going to leave until he had his blessing,” says Donald Metzger, a top financial adviser on McIntyre’s team.

For all his bonhomie, McIntyre, the broker king, sometimes has to watch what he says, lest the corporate compliance folks fuss and grumble. But his alter ego, McGregor, the hero of his novels, can blast away.

In McIntyre’s first novel, “Insiders,” published in 2011, McGregor channels McIntyre’s pique at largely unregulated corners of the markets that contributed to the financial apocalypse of 2008. The villain in “Insiders” and in McIntyre’s new book is a rogue billionaire hedge fund manipulator who taunts the hero/broker with pathological phone calls and holes up in a mansion in Cuba.

It helps to have uber-best-selling authors, such as David Baldacci, as clients. At his first-ever book party, Baldacci’s wife, Michelle, leaned over and whispered to him about which page he was supposed to sign, McIntyre recalls.

One recent afternoon at Equinox, the upscale downtown Washington power-lunch hub, celebrity chef Todd Gray comes out of the kitchen to greet McIntyre at his table, naturally.

“I thought I might get a free lunch since I mentioned the restaurant in my book,” McIntyre yuk-yuks to him.

Gray, whose cousin is on McIntyre’s brokerage team, just smiles.  

Once he’s talking about his books, McIntyre allows himself a bit of latitude, complaining about the “misuse of power” he’s observed over the years in Washington.

“You see sort of the climbers that are seeking power,” he says. If you talked with almost any members of Congress, he says, they would be likely to vouch for entitlement reforms. But they worry and do little, he says, because they know “you’re going to have AARP on your back.”

What would grandpa, a right-hand man of the father of the New Deal, think about all this?

“Do you think he’s turning over in his grave?” McIntyre asks.

There’s no need to answer.

“Are we the 1 percent?” says McIntyre, who is donating proceeds from his new book to charity. “Sure we are. But if we are enhancing people’s lifestyles, enabling them to have a comfortable retirement, pay for their college education, and we’re getting reviled for that, it’s worth it.”

The famous athletes he represents are particularly vulnerable. Everyone’s got a deal for them.

“You look around at all the horror stories,” says Donald Dell, the former Davis Cup captain, tennis TV commentator and renowned sports agent who is a McIntyre pal and neighbor. “They have not kept track of their money. The smart ones want to be stable and solid.”

Over the years, McIntyre says he has steered clients away from dubious investments in everything from thoroughbred racehorses to puppy farms. 

“Money is the last taboo. They’d rather talk about their sex lives than money,” McIntyre says. “Unsophisticated people are easier to deal with unless they think they’re sophisticated.”

McIntyre can ponder all of this on his choice of many, many fields of green. He is, after all, a member of three country clubs — Congressional, as well as clubs near his vacation homes in Naples, Fla., and Bethany Beach, Del. He jokes that he wants to be the worst golfer at three of the best clubs. But Dell — who has referred numerous athletes to his buddy — says McIntyre is actually one of the most competitive people he’s ever met, whether on the golf course or the tennis court, where McIntyre has won club championships.

Their golf matches got so intense that they had to cool things by not giving each other strokes. (They were arguing too much about how many.) Once, Dell says, he nipped McIntyre and collected a $5 bet by kicking his friend’s ball into a sand trap on the 18th hole when McIntyre wasn’t looking.

In the clubhouse afterward, Dell confessed. “Marvin went ballistic!” Dell recalls.

The Three Billion Dollar Man wanted his money.