President Biden’s re-election campaign ended January with nearly $56 million on hand, extending his cash advantage over former President Donald J. Trump, whose campaign had about $30 million available at the end of the month.

That is a jump for Mr. Biden, who ended 2023 with $46 million in his campaign coffers, and a tick downward for Mr. Trump’s campaign, which had $33 million on hand at the end of the year.

Mr. Biden appears to have gained an edge in part because the Democratic Party apparatus, and its fund-raising might, have quickly unified behind him in what is expected to be the most expensive presidential race ever. Mr. Trump, even as he seeks to bring the Republican Party fully on board with his renomination, faces significant questions about the political and financial impact of his many legal troubles.

The apparent disparity in campaign cash, laid out in filings with the Federal Election Commission on Tuesday, does not tell the whole story of how the president and the man he beat in 2020 are raising and spending money as they barrel toward a likely rematch in November.

For one thing, both Mr. Trump and Mr. Biden are raising money through joint fund-raising committees, which do not have to file reports until April. These committees often transfer funds to the campaigns, to pay salaries and buy advertising time. Without those numbers, the candidates’ total financial picture is not entirely clear.

More broadly, the F.E.C. filings on Tuesday point to differences in circumstances.

Mr. Biden, the incumbent, is already raising money alongside the Democratic National Committee, a party juggernaut that can build out a field operation for his re-election bid. On Tuesday, his team reported raising a combined $42 million in January across the committees backing his re-election effort, with a combined total of $130 million on hand at the end of January.

The D.N.C. alone reported $24 million on hand at the end of January.

Mr. Trump, on the other hand, is still fending off a primary challenger, Nikki Haley. Until he wins the nomination, he cannot raise money in tandem with the Republican National Committee. (The R.N.C. on Tuesday reported $8.7 million on hand at the end of January.)

And, perhaps more critically, committees backing Mr. Trump are spending millions each month on legal expenses.

Mr. Trump faces four criminal indictments along with civil cases, which are proving costly. Last year, committees backing him spent at least $50 million on legal expenses, filings show, and those costs are likely to balloon as he prepares for potential trials this year.

Ms. Haley, who has pledged to continue her long-shot bid for the nomination at least until Super Tuesday on March 5, raised significant money in January, even as she lost nominating contests in Iowa and New Hampshire.

But for the first time since she entered the race, her campaign reported spending more than it raised — it took in $11.5 million and spent $13.1 million in January. (Two of the committees backing her did not file reports on Tuesday.)

Her campaign reported $13 million in cash on hand at the end of January, down slightly from $14.6 million at the end of December.

Mr. Biden’s January haul may allay some concerns among his backers that he was not galvanizing enough financial support.

At the end of 2023, the committees backing Mr. Biden had together raised a combined $97.1 million, and had a combined $117 million on hand. It was not the overwhelming advantage some in his party had anticipated, given Mr. Trump’s divisiveness, and the fact that the former president had dedicated resources to primary battles and to his legal expenses.

On Tuesday, Mr. Biden’s campaign manager, Julie Chávez Rodríguez, described his January fund-raising as an “indisputable show of strength to start the election year.”

She added: “While Team Biden-Harris continues to build on its fund-raising machine, Republicans are divided — either spending money fighting Donald Trump, or spending money in support of Donald Trump’s extreme and losing agenda.”

The Trump campaign had $30.5 million on hand at the end of January, but also listed about $1.1 million in debts, which was offset by $490,000 in money owed to the campaign. The campaign raised $8.8 million in January, and spent $11.4 million.

Mr. Trump has raised money for his campaign primarily through the Trump Save America Joint Fund-Raising Committee, which did not file on Tuesday. The joint fund-raising committee raised $75.2 million in the second half of 2023, and spent $77.3 million, ending the year with $3.6 million on hand.

The January report for one of Mr. Trump’s committees — the leadership PAC Save America, which he has used to pay his legal bills — reported $6.3 million on hand at the end of January. The group spent nearly $3 million in January on legal bills, and also owes more than $1.8 million to the lawyers representing Mr. Trump in his various criminal and civil cases, its filing shows.

A spokesman for Mr. Trump, Steven Cheung, responded to a request for comment by sending a link to a Fox News article, which reported that Mr. Trump was expected to raise more than $6 million at a fund-raiser in South Carolina on Tuesday night. (Mr. Biden has high-dollar fund-raisers planned in California this week.)

Save America reported $5,008,508.87 in receipts in January — $5 million of which was a transfer from MAGA Inc., a super PAC backing Mr. Trump. As The New York Times reported last month, transfers of about that size have been happening monthly, part of a huge refund of money from the super PAC to the committee.

MAGA Inc. ended January with $19.7 million on hand, down from $23.3 million at the end of December.

Of the $7.4 million MAGA Inc. raised in January, $5 million came from Timothy Mellon, a banking heir and businessman who has now given a total of $15 million to MAGA Inc.

Mr. Mellon has also caught the eye of Democrats wary of third-party spoiler challenges to Mr. Biden by giving $20 million more to a PAC supporting Robert F. Kennedy Jr., the political scion and Democrat-turned-independent running for president.