THE CROWDED field of candidates for D.C. mayor opens up the possibility that the winner of the upcoming Democratic primary will have less than a majority of votes. Perhaps as little as 30 percent of the total vote could spell victory. Obviously, that would not be ideal. More people voting against the winner than for the winner seems a strange way for democracy to operate.

While it is too late to change the rules for this year’s elections, the District’s political leaders need to look ahead to future contests and put in place reforms that require a majority vote.

The problematic nature of plurality contests can be seen in a recent Post poll showing the front-runner in the April 1 primary, Mayor Vincent C. Gray (D), with 27 percent of the likely vote and his three main challengers — D.C. Council members Jack Evans (Ward 2), Muriel Bowser (Ward 4) and Tommy Wells (Ward 6) — each with 12 or 13 percent of the likely vote. It’s still early in the campaign, and much can happen. Indeed, we are reminded that the last time the District had a multiple-candidate field for mayor, in 1998, then-Chief Financial Officer Anthony A. Williams captured 50 percent of the vote.

But it’s troubling that candidates can be elected to public office with as little as a third of the vote — as happened in last year’s special election for an at-large seat on the D.C. Council — or that incumbents are returned to office only because the opposition vote is split between challengers. Some cities, including New York and Boston, require runoff elections if a certain percentage of the vote is not attained. Runoffs provide a second look for voters, but they have their disadvantages, including extra election costs.

Other jurisdictions have moved to instant runoffs that allow voters to rank candidates rather than choosing just one. This system produces a winner acceptable to the widest share of the voting population, and it has changed the way candidates campaign. The “race to the base” — which is all too evident in this year’s mayoral contest — has been replaced by the need to appeal to a broader swath of voters.

Voting reform is always a challenge. The need becomes most apparent right before an election, the very time when it can’t be implemented. Once the election is past, people lose interest. Whoever wins the free-for-all in the District this year would nevertheless be right to make reform a priority.