Mayor Eric Adams of New York was again denied public matching funds for his re-election campaign on Wednesday, a major setback as he competes against former Gov. Andrew M. Cuomo to emerge as the strongest challenger to Zohran Mamdani, the Democratic nominee.

The city’s Campaign Finance Board said that Mr. Adams was not eligible for public funds because his campaign had provided “incomplete and misleading” information, and the board believed that the campaign had violated the law.

The board did not provide details about its findings, but said the decision was based on “all of the available evidence, including but not limited to its own independent investigation.”

Todd Shapiro, a spokesman for Mr. Adams’s campaign, called the decision “vague and unsubstantiated” as well as “deeply concerning and potentially damaging.”

“We strongly disagree with the Campaign Finance Board’s decision and reject both the tone and substance of its statement,” Mr. Shapiro said.

The board denied Mr. Adams’s request for public funds after he was indicted on federal corruption charges late last year. That decision prevented him from receiving millions of dollars under the city’s program, which gives qualifying candidates an eight-for-one match of small-dollar donations.

Mr. Adams sued the board in May in an effort to overturn the ruling after his charges were dropped by the Trump administration. The lawsuit was dismissed last month, with a federal judge noting that Mr. Adams had been late to provide information regarding conflicts of interest and that more information was still outstanding.

The federal indictment accused Mr. Adams of soliciting and accepting straw donations for both his 2021 campaign and his 2025 re-election campaign. Prosecutors said that he conspired with foreign nationals to illegally funnel money into his campaign coffers.

The board’s latest decision comes as Mr. Adams and Mr. Cuomo squabble over who is best positioned to beat Mr. Mamdani in the general election in November. Mr. Adams and Mr. Cuomo are both running as independents and courting wealthy donors.

Mr. Mamdani was approved for an additional $1.6 million in public matching funds on Wednesday; he previously unlocked millions of dollars in matching funds. Curtis Sliwa, the Republican nominee, will receive nearly $2 million in matching funds in his first payment after qualifying for the money. Jim Walden, a lawyer who is running as an independent, received an additional $237,000.

Mr. Cuomo, who chose to run in the general election after losing the Democratic primary to Mr. Mamdani, was not approved for matching funds on Wednesday. Rich Azzopardi, a spokesman for his campaign, said Mr. Cuomo had paused his fund-raising after the primary, and that now that he is raising money again, the campaign expects to receive a payment at the next deadline.

Mr. Cuomo met with business leaders on Wednesday morning at 45 Rockefeller Center in Manhattan to make a case for his path to victory, according to five people who attended the meeting. Roughly 50 executives attended the fireside chat, which was hosted by the Partnership for New York, a group that represents some of the city’s most powerful business leaders.

Many in the group were alarmed by Mr. Mamdani’s momentum but unsure about whether there was a clear path to beating him, given his strong performance in the June primary. They were also worried about the prospect that Mr. Adams and Mr. Cuomo might split the votes of those who oppose Mr. Mamdani.

Mr. Cuomo candidly addressed his loss to Mr. Mamdani right off the bat, three attendees said, acknowledging that he had not given the primary campaign his all. He argued that he was embracing new strategies and noted that he had been campaigning throughout the city more than before.

Mr. Cuomo brought along the pollster Douglas Schoen, who recently joined his campaign and worked on the presidential campaign of Michael R. Bloomberg, the attendees said. Mr. Schoen highlighted Mr. Adams’s flagging poll numbers and data regarding negative views of Mr. Mamdani. Mr. Cuomo cautioned donors about giving to Mr. Adams in what could be a potential “suicide mission,” one of the attendees said.

Many of the attendees were interested in Mr. Cuomo’s proposal that either he or Mr. Adams should drop out in September, depending on which of them is polling better. (Mr. Adams has not agreed to the plan.)

Albert Bourla, the chief executive of Pfizer and one of the event’s moderators, asked Mr. Cuomo how his plan would work logistically, one of the attendees said.

The executives also asked Mr. Cuomo how he would ensure that New York maintains its competitiveness in the financial services industry as Texas and Florida vie for business, according to four people in attendance. Mr. Cuomo mentioned initiatives like working with artificial intelligence companies and increasing incentives to keep financial firms in the city, but he did not put forward a specific plan, the people said.

Mr. Cuomo pledged to release more detailed policy proposals after Labor Day, one of the attendees said.

While Mr. Adams has relied on his bully pulpit as mayor to highlight his record on crime and affordable housing, Mr. Cuomo has been appearing more frequently in public and agreeing to more media interviews than during the primary. Mr. Cuomo has also been active on social media in recent days, offering one-liners and mixing it up with his critics.

Mr. Cuomo’s campaign criticized Mr. Mamdani on social media on Wednesday, calling him a “do-nothing assemblyman.”

“I’ve built more airports than you’ve passed bills,” read one post from Mr. Cuomo.

Another post bragged about his tireless work ethic, saying, “I don’t think I’ve taken a nap since the 80s.”

Mr. Mamdani has defended his record as a state lawmaker and argued that while Mr. Cuomo spent many years in government, he has a poor record and failed to address the city’s growing affordability crisis.

Mr. Azzopardi joked that Mr. Cuomo’s posts were being written by A.J. Parkinson, a fictitious commentator created by Mr. Cuomo’s father, former Gov. Mario M. Cuomo. He declined to reveal the author of the posts, but said the campaign would make a staffing announcement soon about “new blood.”

When one critic with the username “Andrew Cuomo is a sex pest” wrote that he begrudgingly liked the former governor’s new campaign logo, Mr. Cuomo’s account responded: “Thank you we worked hard on it.”

Another person wrote to him: “I was not familiar with your game.”

Mr. Cuomo’s account replied, “Just getting started."