In the New York City mayoral race, where there are at least 30 declared candidates, if one of the lesser-known entrants drops out, will it make a ripple?

Zach Iscol hopes so.

Mr. Iscol is ending his long-shot bid for mayor, amid hopes that he can make more of an impact as a new candidate in the city comptroller’s race.

Mr. Iscol’s odds will certainly improve: Eight other comptroller candidates have filed paperwork with the city Campaign Finance Board, though one has already dropped out; of those remaining, only two — Brad Lander, a Brooklyn city councilman, and Brian A. Benjamin, a state senator — have met the minimum thresholds to receive matching public funds.

Mr. Iscol had hoped that his moderate brand of Democratic politics and history of public service in the military and in the nonprofit world would attract a following. But he was unable to gain much traction and said he decided that he and New York might be better served if he shifted his focus to another race.

“There are some amazing people who would be history-making in becoming mayor — people of color, women, women of color, people with various ideologies and backgrounds and experiences,” Mr. Iscol said in an interview. “It’s a strong field, and I’m confident in that field we will end up with a good mayor. I don’t see the same happening in the comptroller’s race.”

The mayoral field remains unsettled. Candidates such as Eric Adams, the borough president of Brooklyn, and Scott M. Stringer, the comptroller, are leading the field in fund-raising. Raymond J. McGuire, a former Wall Street executive, recently raised $5 million in three months and appears to have support from the city’s business community.

Andrew Yang, a former presidential candidate, has attracted a lot of attention with his entrance into the race and is expected to be a competitive fund-raiser. Maya Wiley, a former commentator on MSNBC, shored up her campaign by meeting the matching funds threshold. Dianne Morales, a former social services executive, has attracted support with her staunch support for defunding the police.

Other candidates for mayor include Shaun Donovan, the former federal housing secretary; Carlos Menchaca, a councilman from Brooklyn; and Kathryn Garcia, the former sanitation commissioner.

Mayor Bill de Blasio and Mr. Stringer cannot run for re-election because of term-limits laws.

Mr. Iscol, a former marine who often speaks about his combat experience in Iraq, entered the race for mayor in October but said he wishes he had launched his campaign earlier. He still did well in fund-raising for a little-known candidate: His most recent filing showed that he had raised $746,000 and missed the $250,000 threshold to receive matching public funds by about $20,000.

Mr. Iscol will be able to use the money he raised while running for mayor in the comptroller’s race, according to the campaign finance board. He has already probably met the lower threshold to qualify for matching funds for that race, pending an audit by that board, as has Assemblyman David Weprin from Queens, another candidate for comptroller.

Because the race for mayor is far from decided, voters may not treat Mr. Iscol’s departure from that race as a negative in the comptroller’s contest, said Bruce Gyory, a Democratic strategist.

“I don’t know if he’s the last, but he’s smart to be the first,” Mr. Gyory said. “The mayor’s race is so crowded with major figures that someone like Iscol would have been crowded out.”

There are several established candidates in the race for comptroller, including Mr. Lander, Mr. Benjamin, Mr. Weprin and Kevin Parker, a state senator from Brooklyn.

But it is unlikely that any can claim Hillary Clinton as a mentor, as Mr. Iscol can.

Mr. Iscol is friends with Chelsea Clinton, and his mother, Jill Iscol, has been an adviser to Ms. Clinton.

“I’ve known Zach Iscol for over two decades, and he comes at everything from the mind-set of ‘How do we bring resources and assets together to solve problems and address inequities,’” Ms. Clinton said in a statement. “He’s done it at the community level, the national level and in combat zones. He’s got a big heart and is indefatigable when he puts his mind to something.”

Mr. Iscol isn’t the only new entrant to the comptroller’s race. Michelle Caruso-Cabrera, a former anchorwoman for CNBC who unsuccessfully challenged Representative Alexandria Ocasio-Cortez in a Democratic congressional primary last year, filed paperwork to enter the campaign on Monday, her campaign confirmed.

Mr. Iscol said he wants to help the city recover economically from the pandemic, with a focus on the performance of city agencies. He cited “allegations of ethics and campaign finance issues” as helping to have motivated him to enter the race. That was a reference to Mr. Benjamin’s campaign, which relinquished nearly two dozen donations after the The City raised questions about their authenticity.

Mr. Benjamin, who is Black, did not take kindly to the remark.

“It’s unfortunate that a very privileged and failed mayoral candidate like Zach Iscol thinks they can step on Black leaders just to advance their own petty ambition,” Mr. Benjamin said in a statement.