Jeffrey Gildenhorn, right, throwing a birthday party in 2005 for then- D.C. Mayor Anthony A. Williams. With Williams, from left, are his mother, Virginia Hayes Williams, and his wife, Diane Williams. (Sarah L. Voisin/The Washington Post)

Jeffrey Gildenhorn, the owner of a popular diner in Washington’s Chevy Chase neighborhood, who also served as the city’s boxing commissioner and had an unsuccessful campaign for mayor, promising to legalize prostitution, died June 28. He was 74.

Mr. Gildenhorn, who had difficulty swallowing because of Parkinson’s disease, had a choking episode at a downtown restaurant, said his brother, Harry S. Gildenhorn. He was taken to George Washington University Hospital, where he was pronounced dead.

Mr. Gildenhorn was a lifelong Washingtonian who, over a 50-year period, operated no fewer than six businesses along a single block of Connecticut Avenue NW, just south of Chevy Chase Circle.

In 1965, he took over Circle Liquors, which had been founded by his grandfather in 1939. He later opened the Fishery restaurant and market and Rossini’s, an Italian restaurant with an attached gourmet store. In 1988, he launched American City Diner.

“A vision came to me out of the blue — to bring a 1950s diner down here to Washington, D.C., an authentic diner,” Mr. Gildenhorn said in a 2015 oral history interview with the group Historic Chevy Chase DC.

Mr. Gildenhorn during his 1998 campaign for D.C. mayor. (John C. Garofalo/For The Washington Post)

He found a diner manufacturer in New Jersey and commissioned the company’s first new stainless steel construction since 1952. Mr. Gildenhorn’s throwback restaurant, with its all-day breakfast menu, milkshakes and meatloaf, along with a jukebox playing hits from the ’50s, became a neighborhood institution.

It also became a gathering place for members of the District’s political and journalistic elite. Entertainers, mayors and at least one secretary of state visited the restaurant, where Mr. Gildenhorn often held court.

Among the many signs at the diner was one that read, “If you don’t like the way I do things, buy me out!”

Mr. Gildenhorn made American City Diner the headquarters of his forays into local politics and sports. In 1989, he led an effort to buy the Atlanta Braves baseball team and relocate it to Washington. With the backing of a deep-pocketed silent partner (never formally identified), Mr. Gildenhorn offered Braves owner Ted Turner up to $80 million for the team.

“I want to make this the challenge of my life,” Mr. Gildenhorn told The Washington Post at the time. “I’m a native Washingtonian, and in the old days of Griffith Stadium my father had season tickets that were so close we could touch the umpires and talk to the ballplayers. I intend to pursue this thing all the way.”

The offer was turned down.

Mr. Gildenhorn, a longtime Democratic activist, was also a friend of the late Marion Barry, who was elected D.C. mayor for the first time in 1978. In the 1980s, the mayor appointed Mr. Gildenhorn to the D.C. Boxing and Wrestling Commission, which he later chaired.

Jeffrey Gildenhorn in 1990. (Ray Lustig/The Washington Post)

In 1993, Mr. Gildenhorn was instrumental in bringing two world championship fights to Robert F. Kennedy Stadium — the first world title bouts to be contested in Washington in decades.

When Barry ran for a fourth term in 1990, Mr. Gildenhorn was one of the mayor’s top campaign officials, but the reelection effort ran aground after the mayor was arrested while smoking crack cocaine in a Washington hotel room.

By the time Barry won reelection in 1994, he and Mr. Gildenhorn had parted ways. Declaring that the District needed a businessman to lead the government, Mr. Gildenhorn invested $200,000 of his own money in a quixotic race for mayor in 1998.

One of his chief campaign pledges was to legalize prostitution, on the grounds that policing it was a waste of time. He recommended the establishment of legal brothels as new sources of tax revenue.

“I’m taking a logical, realistic approach to solving a major problem that other candidates shy away from,” he said at the time. “I haven’t gotten one negative. I haven’t had one person come and say, ‘How dare you?’ ”

Mr. Gildenhorn lost in the Democratic primary, but he also made news as the only mayoral candidate who publicly contributed to the campaign of one of his opponents — a $500 donation to the eventual winner, Anthony A. Williams.

Jeffrey Nelson Gildenhorn was born Jan. 27, 1943, in Washington. His father was born in Poland and came to Washington with his family in the 1920s.

The younger Mr. Gildenhorn was a graduate of Coolidge High School and, after a preparatory year at the private Bullis School, entered Georgetown University. After his father died in 1965, Mr. Gildenhorn left college to take over management of the liquor store.

He had a flair for the dramatic and, in the 1980s, wrote a couple of screenplays that were never produced. One of them, called “Jeffrey’s Block,” was a farce about the owner of several restaurants who was constantly sneaking through kitchens and back alleys while entertaining a different woman at each establishment.

His marriage to Maxine Lewis ended in divorce. Survivors include his brother, of Rockville, Md.

Mr. Gildenhorn was a member of B’nai Israel congregation in Washington and many civic groups.

In 2003, after a nearby movie theater closed, Mr. Gildenhorn began screening classic movies free at his diner. One sign he posted read, “Not just a restaurant but a way of life.”

Throughout the 2016 presidential campaign, Mr. Gildenhorn used an outdoor sign at his diner as a changing billboard to lambaste the Republican candidate, with such slogans as “Humpty Trumpty will have a good fall.”

Other signs Mr. Gildenhorn posted included one referring to his short-lived political career: “I may not have been elected mayor, but I’m still serving the people.”

An earlier version of this story, based on information from Mr. Gildenhorn’s family, incorrectly stated that he was never married. His marriage, to Maxine Lewis, ended in divorce.