James A. Johnson, a former Democratic campaign operative who led Fannie Mae in the 1990s and transformed the mortgage giant into a political powerhouse, ushering in an era of striking profitability and opulence that the 2008 financial crisis ended by forcing a federal takeover and bailout, died Oct. 18 at his home in Washington. He was 76.

The cause was complications from a neurological condition, said his son, Alfred.

A low-key Washington insider — “I would discreetly characterize myself as discreet,” he once said — Mr. Johnson was averse to publicity. But for years, he played an outsize role in the city’s business, political and cultural life, simultaneously chairing the John F. Kennedy Center for the Performing Arts, the Brookings Institution think tank and Fannie Mae, which helps fuel the housing industry by buying home loans and packaging them into securities.

His reach extended so far that Harold M. Ickes, President Bill Clinton’s deputy chief of staff, once joked that Mr. Johnson was “the chairman of the universe.” While serving as chairman and chief executive of Fannie Mae, politicians on both sides of the aisle praised his stewardship of the institution and efforts to promote homeownership, which Mr. Johnson considered a vehicle for social improvement.

Mr. Johnson, whose father was speaker of the Minnesota House of Representatives, enjoyed a long association with Walter F. Mondale, the U.S. senator from Minnesota who became Jimmy Carter’s vice president. He chaired Mondale’s White House campaign in 1984, which ended in a landslide loss to incumbent Ronald Reagan.

Along the way, Mr. Johnson cultivated connections that increased his clout and prominence. He co-founded a political consulting firm with Richard C. Holbrooke, the Democratic foreign policy adviser and diplomat, and sold it to the investment banking firm Shearson Lehman Brothers, where he was working when he met David O. Maxwell, the head of Fannie Mae, at a dinner party around 1985.

The company, formally known as the Federal National Mortgage Association, appeared to be at a crossroads. Formed by the federal government during the New Deal, it had been owned by private shareholders for the previous two decades but still maintained benefits because of its congressional charter — not least, an implicit guarantee that the government would bail it out of trouble if necessary, enabling it to borrow at favorable rates.

As the Reagan administration mulled privatizing Fannie Mae altogether, Maxwell enlisted Mr. Johnson to analyze the potential repercussions for the company. His work helped stave off privatization and earned him the chief executive’s trust, leading Maxwell to bring him on as vice chairman and heir apparent in 1990. He was elevated to chairman and CEO the next year.

Mr. Johnson set about expanding the company’s portfolio, leveraging his political connections and turning a sleepy, quasi-public mortgage utility into “the largest and most powerful financial institution in the world,” according to “Reckless Endangerment,” a 2011 account of the financial crisis by Gretchen Morgenson, a Pulitzer Prize-winning business journalist, and Joshua Rosner, an expert on housing finance.

From the start, he worked to ensure that Fannie’s lucrative government privileges remained in place and that new regulations were not overly burdensome. A 1992 law signed by President George H.W. Bush was heavily shaped by Mr. Johnson and the army of lobbyists he deployed on behalf of Fannie.

Drafted in the wake of the savings-and-loan crisis, the Housing and Community Development Act aimed to reduce the chance of an expensive taxpayer bailout if Fannie and Freddie Mac, its smaller brother, had bad loans on their books. The law created a new regulatory agency that the mortgage companies helped ensure was “a weakling,” according to Wall Street Journal reporter James R. Hagerty’s 2012 book, “The Fateful History of Fannie Mae.”

It also permitted Fannie to hold far less capital than most banks and created a new affordable-housing focus for the company, requiring it to use its mortgage purchases to help low-income and “underserved” families who previously had been unable to afford homes. Fannie began acquiring mortgages with lower down payments, and Mr. Johnson spoke glowingly of the “revolution” in homeownership that his company helped fuel.

“We think everything gets better with more homeownership. . . . And we have been working very aggressively on that,” he told The Washington Post in 1998. He and his industry had increasingly reached out to poor and moderate-income home buyers, including African Americans, Hispanics and “new immigrants,” he added. “And it’s working. We have systematically reduced the level of down payment required.”

Under Mr. Johnson, Fannie encouraged an automated lending process that relied heavily on credit history to determine loan terms and eligibility. It also embraced Countrywide Financial, a fast-growing lender that became its biggest mortgage provider and emerged as a key player in the subprime lending crisis after all but abandoning loan standards.

In part as a result of those changes, Fannie’s net income more than tripled from $1.17 billion in 1990 to $3.91 billion in 1999, the year after Mr. Johnson retired. He reaped a fortune from the company’s growth, earning about $100 million over nine years, which he defended as comparable to compensation earned by other financial industry executives.

The company’s abundant earnings and executive salaries at times drew scrutiny. A report from the Congressional Budget Office showed that while the implied debt guarantee saved Fannie Mae $3.9 billion in reduced funding costs in 1995, the company retained $1.4 billion of that money in the form of profits, rather than passing it on to homeowners.

Mr. Johnson was able to sideline most of Fannie’s critics, in part through what former congressman Jim Leach (R-Iowa) called “the greatest, most sophisticated lobbying operation in the modern history of finance.”

The company — in some cases, its foundation — contributed to political campaigns and groups such as Acorn and the Congressional Black Caucus Foundation; filled its ranks with former public officials from both parties; funded academic studies that defended its work; and opened more than 50 “partnership offices” across the country, where Mr. Johnson touted billion-dollar “affordable financing” programs in photo shoots with politicians.

Some of Fannie Mae’s profits were given to charities in Washington and elsewhere, and Mr. Johnson personally donated to organizations such as the Kennedy Center, where he created and endowed the Millennium Stage program of free evening performances.

Summing up Mr. Johnson’s tenure, Hagerty wrote that he “presided elegantly over a fleeting period in which Fannie was at the apex of its power, able to please shareholders with ever-larger profits while crushing most of its political enemies.”

Mr. Johnson had joined the board of Goldman Sachs by the time Fannie Mae was rocked by a multibillion-dollar accounting scandal in the early 2000s. His successor, former White House budget director Franklin D. Raines, bore the brunt of the criticism for the accounting mess and, along with two other Fannie Mae executives, reached a settlement with the government; Mr. Johnson was not personally implicated.

He was also far from the scene when Fannie and Freddie collapsed and entered conservatorship during the 2008 financial crisis, leading to a $191 billion bailout that has been repaid. But in both cases, he was blamed in part for promoting a hard-edge corporate culture and aggressive tactics that contributed to the turmoil.

“I sort of characterize Jim Johnson as corporate America’s founding father of regulation manipulation,” Morgenson told NPR in 2011. “This is a person who really, really wrote the blueprint for how to neutralize your regulator, how to manipulate Congress to get your way and, you know, essentially how to destroy your critics.”

Mr. Johnson seldom addressed such criticism in the wake of the financial crisis. But while leading Fannie, he insisted that the company’s “broad political support” was simply the result of its success in promoting “more homeownership for more people at a lower price.”

“Fannie Mae,” he told the New York Times in 1997, “is an instrument for improving the opportunities for Americans that is almost unrivaled.”

James Arthur Johnson was born in Benson, Minn., on Christmas Eve in 1943. His mother was a schoolteacher, and his father — the son of Norwegian farmers — was a real estate broker and leader of the state’s Democratic-Farmer-Labor Party.

Mr. Johnson studied political science at the University of Minnesota, where he was elected student body president and graduated in 1965, and he received a master’s degree in public policy from Princeton University in 1968.

By then, he had immersed himself in the civil rights and anti-Vietnam War movements, driving to Alabama to march with the Rev. Martin Luther King Jr. from Selma to Montgomery. He attended a gathering of antiwar activists on Martha’s Vineyard, Mass., where he roomed with a young Rhodes scholar named Bill Clinton.

In 2004, he chaired the vice-presidential selection committee for Democratic candidate John F. Kerry, with whom he vacationed in Idaho. He briefly held a similar role for Barack Obama in 2008 before stepping down as a campaign adviser, following reports that he had received preferential loan rates from Countrywide Financial.

Mr. Johnson’s marriages to Katherine Marshall and Maxine Isaacs, former press secretary to the Mondale campaign, ended in divorce. In 2016, he married Heather Muir Kirby, a managing director at Deutsche Bank. In addition to his wife, survivors include a son from his second marriage, Alfred Johnson, also of Washington; a sister; and a grandson.

After retiring from Fannie, Mr. Johnson served on the boards of companies including UnitedHealth Group, KB Home and Target and was vice chairman — with Holbrooke — of the Washington private-equity firm Perseus. Since 2011, he chaired the advisory council of the Stanford Center on Longevity, which promotes research into longer, healthier and more rewarding living.

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