I find it hard to take seriously one of the stories that has titillated Washington this week: the story that some of D.C. Mayor Marion Barry's "closest advisers" have been urging him to step down in order to keep from being indicted for corruption.

I'm not saying The Washington Times reporter made up the report that has had the city buzzing. There might well have been an adviser or two to float the idea of offering U.S. Attorney Joseph diGenova an I'll-quit-if-you-drop-your-investigation deal. But surely the tiniest reflection would have suggested that such an offer would make no sense.

It would be a bad deal for the mayor, whose capacity for shaping public opinion would be vastly reduced. Such a resignation under fire, tantamount to a confession of criminal wrongdoing, would leave him jobless, and it would saddle him with legal expenses that now are borne bythe city. The only way it would make any sense at all is as a way of avoiding jail.

But if diGenova has the evidence to put him in jail, why would he accept the deal? As things are now, the prosecutor, widely accused of carrying on a personal vendetta against Barry, can claim political disinterest. He can say, with some credence, that his only interest is in justice.

But if he bought the deal these "closest advisers" of Barry are supposed to be urging, diGenova would be announcing that the motivation for his two-year investigation of the city administration was primarily political all along: aimed not at justice but at getting rid of the mayor. It would be a bad deal for the prosecutor.

But there is a second story whose validity I don't doubt: that several local Democratic leaders have been discussing the problem of a Barry successorship.

It's such a natural political question that party leaders would be derelict not to discuss it. Barry is in the first year of his third term, and there is widespread speculation that he won't seek (or couldn't win) a fourth term. Who would succeed him?

In addition, there is the pragmatic question that arises from the fact that the party leaders cannot know the nature of diGenova's evidence (actual or prospective) against Barry, several of whose aides already have been convicted of corruption. They have to take into account the possibility that Barry might fall, and that makes the question of successorship all the more urgent.

The real story, the one I find most dismaying, is the thinness of the list of possible successors.

The most obvious prospect is D.C. Council Chairman David Clarke, whose chances would increase dramatically in the event of a Barry conviction or resignation, since he would assume the role of acting mayor.

But Clarke has a couple of strikes against him. The less important one involves his present job: his failure to place his personal stamp on the council and his rather mediocre legislative record. His more important handicap is race. Clarke is white in a town where most of the voters are black and where many of them are convinced that white people have laid secret plans for "taking back" political control.

I've heard countless conversations that began with categorical opposition to relinquishing control of the city to a white mayor and then foundered on the question: Then who?

Former council chairmen Sterling Tucker or Arrington Dixon? But Clarke already has defeated them, and they are virtually retired from the political scene. Council members John Wilson or John Ray? Not really; too lightweight. Council member Charlene Drew Jarvis? Crippled by her association with Woody Boggs. Former secretary of the Army Clifford Alexander? He hasn't paid his local political dues.

Well, who else? Walter Fauntroy would be loath to leave his safe congressional seat. No school board member has sufficient political support. Former school board president David Eaton? Floretta McKenzie, who recently announced plans to quit her school superintendent's post?

It's a pitifully shallow pool, something the supporters of statehood for D.C. (with its requirements for representatives, senators and a governor) might be thinking about.