D.C. mayoral candidates Muriel Bowser, David Catania and Carol Schwartz. (The Washington Post)

Democratic nominee Muriel E. Bowser has emerged from a contentious summer on the campaign trail with a hefty advantage in the race for D.C. mayor, holding a double-digit lead over two independent rivals, according to a new NBC4/Washington Post/Marist poll.

Bowser has the support of 43 percent of likely voters, with fellow D.C. Council member David A. Catania following with 26 percent and former lawmaker Carol Schwartz with 16 percent.

The poll follows weeks of speculation about whether this year’s contest is on track to become the most competitive general election for mayor in the District’s 40-year electoral history. And it does not entirely answer the question: Although Bowser’s lead gives her a comfortable edge in the three-way contest, the poll revealed several weaknesses for her — and opportunities for her opponents.

The survey includes evidence of some voter doubt about Bowser’s readiness to assume the mayoralty and her vision for the city. But likely voters rate her more personable and a more effective leader than her opponents, and she leads on two issues poll respondents say they are most concerned about — the economy and education.

The dominance of Democratic voters, who make up the vast majority of the D.C. electorate, continues to weigh in Bowser’s favor. Her rivals have tried to chip away at the advantage, with Catania circulating “Democrats for David” yard signs, but Bowser has retained the loyalties of about half of Democratic voters — including nearly half of those who supported incumbent Vincent C. Gray in the primary — while independents are evenly split among the three candidates.

Muriel Bowser leads D.C. Mayor's race

Willis Thomas Jr., a 49-year-old fire department captain and Democrat who lives in Brightwood, said his vote is Bowser’s to lose. “I don’t just vote for Democrats; I have to hear from every side,” he said. “But . . . the chance of me voting Democratic is high unless they mess things up based on what they do in their campaign.”

Thomas said he was impressed by the background of Bowser, the only candidate born and raised in the District. “I think she cares about what’s going on, about the people in the city,” he said. “She kind of had a middle-class background. I think she understands a lot of that. Can she do the things that need to be done to fix the problems? Who knows?”

Opportunity for opponents

The poll casts doubt on the prospect that a surge in independent or Republican voters could help Catania or Schwartz overtake Bowser in a city in which three in four voters are registered Democrats. Non-Democrats account for only 23 percent of likely voters identified in the survey.

Yet the poll found room for either Catania or Schwartz to steal a significant share of Democratic support from Bowser. About one in four Democratic likely voters currently support Catania, and two in three Democrats say they would “somewhat seriously” consider voting for a non-Democrat.

Bowser, who represents Ward 4 on the council, earns the support of less than two-thirds of the primary voters who backed her five months ago when she defeated Gray. Since a Washington Post poll in March asked voters about a Bowser-Catania matchup, she has weaker support across the city, especially among registered Democrats, white voters, younger voters and women.

Voters think that Catania, an at-large council member since 1997, has about as much experience and as compelling a vision for the city as Bowser. But Catania has not capitalized on Bowser’s weaknesses.

Since the Post’s March poll, which took place a month after he entered the race, Catania’s share of the electorate has barely budged. He has no advantage among independents, and crucially, he has not staked a claim on the issue of education — which he has made the cornerstone of his campaign. He trails Bowser, 40 percent to 30 percent, among likely voters who say education is the most important issue in the race. Fourteen percent of those voters favor Schwartz, who has also highlighted her education platform.

Looking at where key candidates stand on pressing issues facing Washington.

Additionally, Catania’s reputation for a confrontational style appeared to register in the poll, with just 19 percent of likely voters saying that Catania has the best temperament to be mayor. In contrast, 40 percent say Bowser has the best temperament, and 23 percent choose Schwartz.

John Whall, a 53-year-old health management executive who lives in the U Street area, said he has ruled out a vote for Catania based on personality concerns. “I have personal experience and anecdotal experience, and he’s not someone I want running the government in any shape or form,” he said. “Ultimately, your job is to make the process work. He gets an idea in his head or a notion in his head, and that’s it.”

Whall said he has some doubts about Bowser’s readiness, but he said, “She’ll hopefully muddle along and figure it out. I think she’s young, and I think she’s smart, and I think she’s been in the city.”

Renewed campaign efforts

The NBC4/Washington Post/Marist poll was conducted Sept. 14 to 16 among a random sample of 1,249 D.C. adults reached on conventional and cellular phones. The margin of sampling error is plus or minus four percentage points among the sample of 572 likely voters.

The survey was taken at a critical period in the long-percolating mayoral race. With fewer than 50 days until Election Day, the campaigns have started new efforts to make their pitches to voters.

Last week, Schwartz formally kicked off her campaign with a Freedom Plaza rally in which she made the case that she is best equipped to serve as a “bridge” between old and new residents. On Monday, Catania unveiled a lengthy platform, renewing his case that he has the most detailed and ambitious vision for the city. And on Wednesday morning, Bowser debuted radio ads on key African American-oriented stations, using her superior campaign bankroll to shore up support among her base of Democratic voters.

On Thursday evening, the three candidates will meet at American University for their first formal debate — one of four that Bowser has committed to — broadening the race beyond media interviews, voter mail and living room meet-and-greets to give voters a more intimate, side-by-side comparison.

Both Catania and Schwartz have an opportunity in the number of likely voters who don’t know them — 35 percent for him and 36 percent for her. Bowser, in contrast, is unknown by only 28 percent of likely voters.

Concerns that Schwartz could serve as a spoiler for Catania — aired after her surprise entry into the race in June — appear to be unfounded. The 16 percent of likely voters who support her are nearly evenly divided between Catania and Bowser when asked their second-choice candidate in the race.

Instead, the former four-term council member is drawing voters attracted to her unusual, even quirky, profile. “She is a social liberal but a fiscal conservative,” said Carrie Thomas, a 41-year-old financial manager living on Capitol Hill. “That’s me. . . . People can call it a wasted vote if they want, but I disagree. If only four people vote for her, that’s fine.”

Overall, Bowser earns the support of a majority of African American likely voters in the poll, as well as voters making less than $75,000 a year and those who did not complete college. Catania performs the strongest among white voters, with 41 percent of white likely voters supporting him. He and Bowser earn equal support among the more affluent and college-educated. Schwartz narrowly tops Catania among African American voters, only 11 percent of whom support his candidacy in the poll.

Rachel Weiner and Peyton Craighill contributed to this report.