At least one FEC commissioner has already indicated she agreed that if Harris became the nominee she would have legal access to the campaign funds.

“Republicans may be jealous that Democrats are energized to defeat Donald Trump and his MAGA allies, but baseless legal claims — like the ones they’ve made for years to try to suppress votes and steal elections — will only distract them while we sign up volunteers, talk to voters, and win this election,” Harris campaign spokesperson Charles Kretchmer Lutvak said in a statement.

Harris’ campaign said Tuesday it had raked in more than $100 million in new donations between Sunday afternoon and Monday evening, after Mr. Biden ended his bid for reelection and endorsed her. That total includes money raised across Harris’ campaign, the Democratic National Committee and joint fundraising committees.

In Warrington’s complaint, he also accuses Mr. Biden’s campaign of making an excessive contribution to Harris, saying, “This is little more than a thinly veiled $91.5 million excessive contribution from one presidential candidate to another, that is, from Joe Biden’s old campaign to Kamala Harris’s new campaign. This effort makes a mockery of our campaign finance laws.

“Contributions by federal candidate committees to other federal candidates are limited to $2,000. Yet, Biden for President is seeking to make an excessive contribution over approximately $91 million dollars — more than 45,000 times the legal limit.”

In addition, the Trump campaign claims that since Mr. Biden dropped out of the race before transferring the funds to Harris, he’s prohibited from keeping the contributions.

As a remedy, the campaign asks the FEC to “immediately open an enforcement matter, seek to enjoin this unprecedented illegal transfer, assess a civil penalty commensurate with the size and scale of this brazen violation, and refer this matter to the Department of Justice for prosecution as a knowing and willful violation of federal law.”

Ultimately, the campaign contends that, “Kamala Harris is in the process of committing the largest campaign finance violation in American history and she is using the Commission’s own forms to do it. The Commission must not and cannot sit idly by while one candidate takes nearly one hundred million dollars from the authorized committee of another, in violation of the Act and the will of the donors who gave the money in the first place. The Commission must immediately find reason to believe and quickly end this ongoing violation.”

Hans von Spakovsky, a former member of the Federal Election Commission, said in a Fox News op-ed published Sunday that if Harris becomes the presidential nominee, she would get access to the campaign cash.

“When the Biden for President Committee filed its registration statement with the FEC, it registered itself as the ‘principal campaign committee’ for both Joe Biden and Kamala Harris,” he wrote.

Von Spakovsky noted that if any Democrat other than Harris were the party’s nominee, they would not get  the $91.5 million the committee has.

“Biden for President would be limited to giving no more than a $2,000 contribution to the new presidential nominee’s campaign committee,” he said.

Von Spakovsky is not a backer of Harris or Mr. Biden. He is the manager of the conservative Heritage Foundation’s Election Law Reform Initiative and has warned that election fraud is real and can change the outcome of the election. He also authored the FEC section of the Project 2025 policy guide, part of the sweeping presidential transition project overseen by Heritage.

The move by Trump’s campaign comes as his allies have floated the possibility of court challenges to try to keep Mr. Biden at the top of the Democratic ticket, even though he’s ended his campaign. But election law experts believe it’s unlikely such court fights aimed at blocking Vice President Kamala Harris’ presidential candidacy would gain traction in the federal courts.

-Ed O’Keefe, Melissa Quinn and Aaron Navarro contributed reporting.