Mayor Muriel E. Bowser (D) will seek reelection in 2018, asking District voters for a second term that she says will be dedicated to making sure that the District's runaway economic prosperity is shared more equitably across its gulfs of class and race.

Bowser's decision, which she announced in an interview with The Washington Post, was long expected. It nevertheless serves as an unofficial starting gun for the coming campaign season, and throws into relief the stakes of a mayoral campaign in which she so far has no serious challengers — a rarity in a city whose fractious political class rarely shows deference toward incumbents.

"I want to be remembered for having more Washingtonians participate in a fast-growing, changing city," Bowser said. "How can we close the gaps between the haves and the have-nots in our Washington, and let this be a story of true renaissance of the city that focused on bringing everybody along?"

Bowser's reelection campaign will play out as the lines separating those haves and have-nots appear to be hardening. Census data released last week showed that median incomes for black and Latino residents of the District declined over the past year even as it continued to grow for white households, according to an analysis by the D.C. Fiscal Policy Institute.

Median household income for white residents was three times as great as that of black residents in 2016.

For the mayor — whose support is weakest in the poor and predominantly African American neighborhoods east of the Anacostia River — that reality could increase pressure on her to try to reduce income inequality.

That is especially the case when it comes to the District's dearth of affordable housing, which this year surpassed crime as voters' top concern, according to a Washington Post poll in June.

The mayor said that the creation and preservation of affordable housing would remain a top priority in her second term and she expects the District to spend more than $100 million on affordable housing next year.

"We've been better at getting the money out the door," she said. "The bureaucracy has improved, and the [developer] community that spins the money and produces the housing has improved. And they can continue to amp up their capacity if they can rely on the city."

Asked about a central goal for a second term, Bowser demurred, saying that she would devote her time and energy to an array of policies that included improving public transit, reducing income inequality and making the city greener and more energy-efficient.

"No mayor can do one thing," she said. "You do a thousand things all at once."

If reelected, the mayor said that she would pay special attention to the east side of the city, with a focus on increasing homeownership and attracting good-paying jobs. An example, Bowser said, is the "Infrastructure Academy" program she launched this month to train District residents to work in the utility, transportation and logistics industries, as well as others.

While broadly popular, Bowser has often avoided the sort of bold initiatives that inspire passionate support or opposition.

The Post poll showed that Bowser has a 67-percent favorable rating among District residents and was the clear favorite among likely contenders for the mayor's office in 2018. But it also revealed a lack of enthusiasm: Some 20 percent of Washingtonians surveyed said they strongly approved of her leadership, while 47 percent "somewhat" approved.

The most prominent exception to Bowser's cautious approach — her politically risky plan to establish family homeless shelters in all eight wards of the city — was overshadowed by an aspect that called for the city to lease shelter sites from her campaign donors. The D.C. Council ultimately approved a different version that involved building new facilities mostly on publicly owned land, rather than leasing them.

The episode touched on another potential weakness: a perception that Bowser is swayed by political donors. In The Post poll, some 48 percent of D.C. residents rated her negatively for efforts to reduce campaign contributors' influence, while 31 percent rated her positively.

The poll came shortly before D.C. Council member Mary M. Cheh (D-Ward 3) released results of a months-long investigation that found Bowser's top appointee, City Administrator Rashad M. Young, sought to steer a lucrative roadwork contract to one of the mayor's campaign contributors. Bowser dismissed the findings, and Young said he had intervened only to ensure that the contracting process was fair.

Young and a second member of Bowser's cabinet, Deputy Mayor for Greater Economic Opportunity Courtney Snowden, were also identified in May by The Post as part of a group of public officials whose children received preferential treatment in the school-enrollment process from former D.C. Public Schools Chancellor Kaya Henderson, according to a D.C. inspector general's report.

The Post later reported that Snowden was the subject of a second, pending investigation by the inspector general into allegations that she used her staff for babysitting and had improper interactions with private companies that included a client of her former lobbying firm.

Bowser said that despite those episodes, she was confident that voters continue to trust her administration.

"I think people know that I have the highest expectations of everyone who works for me. I expect them to follow the rules," she said. "And if they don't follow the rules, that they can be held accountable."

Bowser so far has no serious opposition. D.C. Attorney General Karl A. Racine (D), one potentially viable challenger to the mayor, announced this month that he would instead run for reelection.

D.C. Council member Vincent C. Gray (D-Ward 7), who served a single term as mayor before Bowser defeated him in 2014, is widely believed to want a rematch in 2018.

But The Post poll showed he may have an uphill battle if he chooses to run. In a hypothetical three-way Democratic mayoral primary, Bowser captured 50 percent of the support among registered Democratic voters, compared to 27 percent for Gray and 10 percent for Racine.

Gray said Friday after Bowser's announcement that he thought the city would benefit from another "credible candidate" in the mayor's race, but declined to say whether it would be him.

"I'm on my own timeline," he said.