A NUMBER of factors combine to make this year’s contest for D.C. mayor unusual. There is the fact that voters are not accustomed to an April 1 primary. There is the difficulty of sorting out a large field of candidates. And there is uncertainty caused by the lingering federal probe into government corruption.

But with less than three months to go the race is starting to take final shape. Voters need to pay attention. Critical issues — improving schools, getting people into jobs, fixing broken neighborhoods — confront the District. What solutions do the candidates offer? What are their chances for success? Who is best suited to lead D.C. into its future?

Nine candidates — including Mayor Vincent C. Gray, four sitting council members, a successful businessman and a former Clinton administration official — filed nominating petitions with the board of elections by last week’s deadline and, barring challenges, will appear on the Democratic primary ballot. Given the historical record and Democrats’ overwhelming advantage in the District, the winner of the primary becomes the favorite to win the general election in November.

Normally, an incumbent with a credible first term like Mr. Gray would be able to make a strong claim to reelection. His steady support of education reforms has helped the city’s public schools. But the evidence of corruption surrounding Mr. Gray’s 2010 mayoral campaign uncovered by the U.S. Attorney’s office is worse than troubling. Mr. Gray has denied any wrongdoing but refuses to discuss details of his first campaign in which four top campaign aides have pleaded guilty to felonies. No matter what federal prosecutors do or don’t do in the coming months (and we hope there is some resolution), the unanswered questions about Mr. Gray’s tainted campaign will give voters serious pause.

All the more reason to pay attention to other credible candidates. Among Mr. Gray’s challengers are capable members of the D.C. Council — Jack Evans (Ward 2), Muriel Bowser (Ward 4) and Tommy Wells (Ward 6) — who are running serious campaigns. Consider, for example, Mr. Evans’s experience and effectiveness as the council’s longest serving member, Ms. Bowser’s leadership in enacting ethics reform and Mr. Wells’s vision for a liveable city.

Early voting will begin March 17. Voters wishing to change their party affiliation have until March 3. This is not an election that anyone who cares about the District can afford to sit out.