MAYOR MURIEL E. BOWSER (D) announced Friday that she is running for reelection, and it marked quite a contrast with her first bid for the office. In 2014, the then-Ward 4 D.C. Council member faced a sitting mayor and a crowded field in a Democratic primary that included three other council members and a prominent businessman. That challenging primary was followed by an unusually competitive general election. This time no credible challenger has emerged, and it is possible — though the primary is nine months away — that it will be an easy glide to a second term for Ms. Bowser.

If that is the case, it will be due in some measure to Ms. Bowser's generally successful three years in office. The District is booming, residents are upbeat about the city's prospects and a Post poll in June showed high approval ratings for the mayor. She is able, as she did in announcing her candidacy, to point to real accomplishments such as progress in combating homelessness, ramping up the availability of affordable housing, and maintaining solid relations between the police department and the communities it serves. Despite an early ethical stumble surrounding an ill-advised effort to establish a big-money political action committee, which she abandoned, she has largely delivered on her campaign promise of a "fresh start" for a scandal-weary city.

Ms. Bowser, 45, the District's seventh elected mayor, would surely welcome an easy path to reelection; but voters, and even office-holders, are better served by a genuine choice that pushes aspirants for office to make their case. With D.C. Attorney General Karl Racine (D) forgoing a rumored challenge to the mayor in favor of running for reelection, the only person mentioned as a potentially plausible challenger is former mayor and now Council member Vincent C. Gray (D-Ward 7). Ms. Bowser bested him in the 2014 race, which was largely defined by the corruption scandal that accompanied his 2010 mayoral campaign. Six of his campaign associates and staffers pleaded guilty to federal charges.

If Mr. Gray were to enter the race — and he has welcomed the speculation — there is the danger of a contest that rehashes old grievances between two politicians who don't much like each other. That would not be in voters' interests.

What needs to be discussed in the months leading to the June 19 Democratic primary — no matter who or how many are on the ballot — is a vision of the city's future that includes improving public education and safety, among other critical areas. Then, too, there is this key challenge: How, in a prospering city, can officials confront gaping disparities of wealth that leave too many people behind or forced out?

The city has lately been inclined to turn its mayors out of office after four years. If reelected, Ms. Bowser would have a rare opportunity to build on the foundation of a first term. Her reputation is that of a competent if at times prickly manager whose cautious, almost businesslike approach to government has featured no grand vision. That's not necessarily a fault. But what does she want to achieve for the city if given another four years?