After nearly four years chairing the D.C. Taxicab Commission, Leon J. Swain Jr. was quietly dismissed Tuesday.

During his tenure, Swain led the city regulatory body through two dramatic events — the deployment of time-and-distance meters in city cabs, replacing the much-hated zone system, and a federal bribery investigation, for which he wore a recording device to gather evidence that led to some 40 arrests.

But it appears Swain couldn’t survive the demands of big-city politicking.

How it went down is pretty simple. Swain got an e-mail on Tuesday morning asking him to come down to the John A. Wilson Building for a late afternoon meeting with City Administrator Allen Y. Lew.

When he arrived, “He had this long look on his face, and I knew what was going to happen,” Swain said of Lew. “He said, ‘It’s never been easy to do this. ...’”

Why it went down is another matter. Lew didn’t give Swain a reason for his dismissal. Tony Robinson, Lew’s spokesman, declined to elaborate.

Swain, of course, has his theories. One involves his participation on the United Medical Center board — serving, in fact, as its chairman until he resigned under pressure from Mayor Vincent C. Gray earlier this year.

But he’s more convinced that his ouster was a political payoff to taxicab owners — particularly Ethiopian-American operators — who had supported Gray’s campaign last year.

“They told me to my face: ‘We paid to get rid of you,’” Swain said. “Maybe they’re still mad about me doing the sting.” He added that he had recent encounters with two Gray aides who referenced the taxi industry’s support when discussing policy matters.

Larry Frankel, a cab driver and organizer who leads the Small Business Association of D.C. Taxicab Drivers, confirms that Gray delivered a personal pledge to fire Swain.

”We’re glad that the mayor finally completed a promise he made to us,” he said Thursday.

Swain’s firing was one of three promises that Gray made to taxi industry representatives during his campaign, Frankel said. The others were to institute a gasoline surcharge — which Gray did last month — and to appoint three industry representatives to the eight-member Taxicab Commission, as required by law. “We’re waiting for him to that,” he added.

Swain earned the industry’s ire in large part, Frankel said, by “persecuting” drivers through a new corps of hack inspectors, who were empowered for the first time under Swain to pull cabs over and issue tickets.

”They physically pulled cab drivers out of their seats and put them across the hood like some sort of criminal,” Frankel said, adding that immigrant drivers, particular, were given “an incredible amount of violations that really weren’t substantiated.”

”It seemed to be a private police force that Mr. Swain was in charge of,” he added. “This man was not easily reined in. He was a renegade or a maverick.”

Swain suggested a more proximate cause for his ouster: Last week, he revealed at a D.C. Council hearing that he had given a list of city-licensed cab drivers and limo operators to the Office of Tax and Revenue, which would in turn hand it to the Internal Revenue Service, which had requested such a list last year. Also last week, he sent notice to taxicab companies that they had until late May to comply with licensing provisions, including a new requirement to submit copies of their income tax records.

Cab drivers and owners, like others businessmen who deal largely in cash, have long been monitored closely by authorities wary of income tax evasion.

Frankel said the drivers he represents, who are interested in running an honest industry, actually supported Swain’s tax crackdown. “But maybe some of the companies and individuals he went after could have had some political pull.” he said. “That could have been.”

The firing did not come as a surprise to Swain, who said that D.C. Council member Marion Barry (D-Ward 8) told him early this year that he was going to be replaced with Novell B. Sullivan, who chaired the Taxicab Commission during Barry’s fourth mayoral term.

Barry said that Swain’s recollection was “not accurate” and that he had urged Gray keep Swain but ceased his support after Swain initially refused to step down from the United Medical Center board.

As for Sullivan, Barry said he told Gray that “Novell Sullivan worked his butt off for the mayor [during the campaign] and would be suitable for some position in the administration.”

Should Sullivan get Gray’s nod, Swain said, “I would be there to testify why he should not be placed on the commission.”

Swain said he is concerned that the FBI probe into the city taxi industry, which is ongoing, might be impeded by his departure — for instance, some sensitive files remain in his office, he said. But he has no regrets about how he handled the job.

”I have my integrity,” Swain said. “I don’t you can find one incident where I did anything wrong. ... I believe in two things: God and the rule of law, and I never wavered between them. Maybe if I wavered, I’d still have the job.”