Mayor Karen Bass of Los Angeles and her onetime ally, Nithya Raman, vied hopefully for a trove of undecided voters on Tuesday as the rival Democrats entered the homestretch in a fierce generational contest for the city’s top political job. With ballots set to be mailed Oct. 1, the appearances in a candidate forum by Ms. Bass and Ms. Raman were their first in a major venue since last week, when a Berkeley IGS/Los Angeles Times poll showed Ms. Raman, 45, significantly ahead of the 72-year-old incumbent. The poll, which Ms. Bass’s campaign dismissed as an “outlier,” showed Ms. Raman with a lead of 39 percent to 28 percent and support from large majorities of younger voters. But roughly one likely voter in three was undecided — a stunningly high figure with only about a month to go before the general election on Nov. 3. The survey was conducted two weeks ago.

“I know that there are a lot of voters out there who are undecided,” Ms. Raman said, making the case that she understood the frustration and distrust in government of many Angelenos. Ms. Bass also appealed to the undecided, saying: “I do understand that Angelenos, and people all around them, are very upset. Life is too unaffordable. People are not feeling safe.”

Paul Mitchell, a Democratic consultant and political data expert who has been tracking the mayoral race, said that those uncommitted voters were both a reflection of voter dismay and a wild card in the race. “I think the deciding vote in this mayor’s race could be the people who decide not to vote,” Mr. Mitchell said.

For more than a year, Ms. Bass has faced an uphill battle for re-election. Her approval ratings have slumped badly since Jan. 7, 2025, when catastrophic wildfires erupted across Southern California while she was out of the country. Ms. Raman, a city councilwoman, endorsed the mayor less than two weeks before jumping into the race in February after it appeared that Ms. Bass might have no serious opposition.