D.C. Council member Phil Mendelson, first white mayor of the District.

Imagine that. The successive string of black mayors dating to home rule in 1973, broken. The collapse of black mayordom in the District — not the job, but the institution, where racial inheritance is a requisite for top leadership. No more.

The prospect is no doubt as uplifting to some as it is depressing for others. Either way, it’s disgraceful how the prize might be lost.

Here’s how it could happen:

A council vote Wednesday makes Mendelson (D-At Large) the chairman, filling the seat vacated by Kwame R. Brown, who resigned last week after pleading guilty to bank fraud. That puts Mendelson in line to succeed Mayor Vincent C. Gray if a federal investigation into his campaign finances turns up enough dirt to force him out of office.

A council vote and a prosecutor’s lightning bolt and Mendelson, 59, makes history, reluctant though he may be to do so.

“At this point, I’d like to see what the investigation uncovers,” Mendelson told me recently. “As long as I have worked with Vince, and I have worked closely with him, I never saw anything that suggested corrupt behavior. So I view what is happening on the council right now as a transition within the council, not a step up to the chairmanship while waiting for the other shoe to drop on Vince. Personally, that’s not my ambition.”

That “other shoe” belongs to U.S. Attorney Ron Machen. And — as Brown, former D.C. Council member Harry Thomas Jr. and a couple of Gray’s campaign aides can attest — a stomp usually ends with a guilty plea, no need for a trial, a resignation from public office and jail time.

When Machen comes calling, people start falling. And, as Mendelson may soon discover, others start to rise.

Before winning a seat on the council in 1998, Mendelson worked for the late D.C. Council Chairman David Clarke (D). Clarke became the first white candidate to win all of the city’s wards. Mendelson became the second. And he’s been a shoo-in ever since.

His only rival for the chairmanship is Vincent B. Orange (D-At Large), who won a special election in April. The vote is expected to be close, but Mendelson’s 14-year tenure gives him the edge.

“Race is still an issue,” Mendelson said. “But the way I look at it, the question is whether a person who seeks support from voters is sensitive to the concerns of voters across the city.”

There are some who say Mendelson fell far short of the mark during a hearing on whether to confirm Betty Noel, who is black, to a seat on the Public Service Commission.

Civic activist Iris Toyer and other black women are especially angry with Mendelson, who voted against Noel.

“As an African American woman sitting in the audience, I heard him say that while Ms. Noel is very talented, smart and knows her stuff she is not sufficiently docile in her dealings with her superiors (white men),” Toyer wrote on a popular e-mail list for Ward 8 residents. “He described her as arrogant, combative, argumentative and dismissive. . . . All I can say is that after sitting through his attack on one of our sisters, I too am now an angry black woman and will not ever cast a vote in his direction.”

Mendelson saw what Toyer wrote.

“I don’t like that fact that there are some long-term supporters who are bitterly upset with men over what they ascribe to me as my reasons for opposing something rather than listening to what my reasons are,” he said. “It’s going to take a long time to rebuild that trust.”

Trust. Mendelson mentions that word a lot.

“What’s bugging people right now is that they have no trust in government, and I don’t blame them,” he said. “Trust is a precious thing: hard to get, easy to lose, even harder to get back.”

Maybe impossible given the kinds of corruption the U.S. attorney has been uncovering.

Unseemly, petty, even silly acts of malfeasance. Embezzling money set aside to provide recreational activities for children. Some of the culprits were well-educated black men who risked their freedom, their families’ well-being — to say nothing of black power and pride — to buy clothes, a car, a boat, a motorcycle.

“I have asked the U.S. attorney if he can, please, move quickly,” said Mendelson, who chairs the Committee on the Judiciary. “It’s very hard on the government when you’ve got this cloud.”

And when the cloud lifts, the city could have its first white mayor.

To read previous columns by Courtland Milloy, go to washingtonpost.com/milloy.