Just 18 months ago, Del. Walter E. Fauntroy was undisputedly the most popular politician in town. He had been reelected two years earlier with more than 80 percent of the vote. He faced no real opposition in his bid for a fifth term. And in a poll taken by The Washington Post to gauge voter sentiment towards prominent figures, Fauntroy placed at the top.

In the months since, Fauntroy's public image has been tarnished by a series of apparent political mishaps -- from a faltering voting rights drive whose troubles are laid to Fauntroy and his unsuccessful efforts to become the "boss" of District politics; to a Mideast peace effort that has angered many politically influential Washington-area Jews; to early flirtations with a presidential endorsement of Sen. Edward M. Kennedy that turned off key city businessmen who support President Carter.

In many states, all this would spell imminent political doom. The young up-and-comers and even some of the old down-and-outers would be lined up for a crack at Fauntroy.

But there is no political threat in Fauntroy's immediate future -- only five virtually unknown persons who have picked up petitions to run against him in the May 6 District Democratic primary. With only four weeks remaining before the petitions are to be turned in, there is little likelihood that a serious challenge to Fauntroy will emerge.

Fauntroy aides Cliff Smith and Eldridge Spearman are confident that the lack of serious opposition is an indication that their boss is much more popular than the press and political pundits would suggest.

But for many other city politicians, including Mayor Marion Barry, there is another reason for the dearth of opposition. Fauntroy's office, they say, has lost its political glow.

The mayor's office now gets much of the attention the delegate received prior to home rule, Barry said, and it is the elected mayor and City Council members who make the rules, run the government and dole out the jobs in the District.

A few weeks ago, others add, there was a feeling that full voting representation would probably come and when it did, the longtime nonvoting delegate would be assured of a coveted seat in the U.S. Senate. Now the full voting effort seems doomed, and the prospect of being a permanent voice without a vote in Congress is unattractive.

"It's a terrible job. It's a dead-end job. It's a great job for a guy who wants to retire," one politically involved lawyer said. "At least a congressman from another state can move up or run for senator."

"A lot of folks are not that excited," said one member of the City Council. "I have more power down here than Walter has up there.

"The general feeling is Walter has screwed up full voting so bad that we're not gonna get it anyway. There is also the belief that if we did, in fact, get two senators and one or two representatives, if you were on the City Council and not up for reelection, you stand a better chance of raising funds than Walter does."

Last year, there was considerable talk of opposition to Fauntroy. Council member John A. Wilson (D-Ward 2) said he was mulling over a challenge, but quietly backed down. Observers said that a major reason was Wilson's own sometimes unpredictable behavior and lack of a base among those voters who were most disgruntled with Fauntroy. a

Council member John Ray (D-At Large) also toyed with the idea. But, Ray said last week, he's too busy this year running for reelection. One of the problems for Ray, sources said, would be lingering suspicions about his base among liberal and affluent whites. If he had gone after Fauntroy, whose Mideast forays had angered many liberal whites, Ray would have been perceived as the white community's headhunter.

The working list stopped there, though some mentioned former mayor Walter E. Washington coming out of retirement to take on his former nemisis. Surely he had the name recognition, they said. But, so far, there have been no indications that Washington intends to reenter the political spotlight.

The lack of opposition to Fauntroy is not merely the question of "buts" and "wells" that some would suggest. A former civil rights activist and Baptist minister, Fauntroy has roots in many of the key constituencies from which his would-be challengers would have to draw support -- ministers, regularly voting churchgoers and former community activists, for example.

And the number of "viable" candidates for the job are restricted to either that handful in the political "in-crowd," or leftovers and never-rans from other campaigns -- Clifford L. Alexander (now Secretary of the Army), Ronald H. Brown (board chairman of the University of the District of Columbia) and Delano E. Lewis (assistant vice-president of C&P Telephone Co.).

The second generation of home rule politicians has yet to emerge clearly.

So, for the next two years at least, Fauntroy seems to be well-entrenched, even though his lofty speeches about the arithmetic of power seldom add up to power-brokering victories; and even though his sometimes sophomoric political antics -- like calling for an investigation of the National Football League "from his helmets to its cleats" after the Redskins lost their final game -- suggest to some that Fauntroy is a delegate whose time has gone.

The money, the workers and the issues that would lead to a Fauntroy defeat are ready and waiting for the right person to come along, local power players contend. But, so far, the right person has not shown up.

And Smith, who is one of Fauntroy's closests political advisers, has a smug smile on his face when he hears the talk of how the delegate's job has lost its glow. Much of the rhetoric is merely a case of sour grapes, he says.

"I don't think the seat has lost any of its attraction," Smith said. "If Walter Fauntroy decided not to run, I'm sure you would have everybody and their momma ready to lay claim on the job."