Donald Trump has been burning through millions of dollars as he faces an onslaught of legal bills from the investigations threatening his presidential election bid -- with some sources of funding drying up fast.

The former US president is hardly strapped for cash, as his joint fundraising committee brought in $54 million during the first half of 2023 -- more than any of his Republican primary rivals in next year's election.

But critics say new financial filings demonstrate how his spiraling legal woes are making a significant dent in a war chest that could be going to TV spots, rallies and other campaign events as he bids for a second term.

The Save America political action committee (PAC) Trump founded disclosed this week that it was down to its last $4 million by the end of June -- loose change in campaign finance terms -- after spending more than $20 million on legal fees.

Trump has a wide berth to spend vast sums on lawyers, and there is no question of criminal wrongdoing in doing so, but Washington watchers have questioned whether campaign donors should be expected to pick up such tabs.

"If you're sending Trump money, it's almost exclusively going to his personal legal fees," said attorney and conservative political writer A.G. Hamilton.

"Which also means they are going to have practically nothing left over for spending on turnout efforts to compete with Democrats in key states."

Trump's latest indictment over his push to overturn the 2020 election will further strain resources, with legal bills now his PAC's largest expense as the billionaire faces indictments in Florida, New York and Washington.

- 78 felony counts -

The Republican National Committee covered most of Trump's legal bills until November last year but stopped when he launched his 2024 election bid.

His various political operations have around $32 million cash in the bank heading towards January's Iowa caucus -- the first nominating contest in the primary season.

Most of the money Trump raises goes directly to his presidential campaign, with just 10 percent going to Save America, which has been covering legal expenses for almost any figure in Trump's orbit ensnared in the investigations.

The PAC, which raises most of its money from small-dollar donations, informed the Federal Election Commission it had given $21.6 million to law firms defending Trump and his allies this year -- $5 million more than its total legal costs in 2021 and 2022 combined.

Estimated by Forbes to be worth $2.5 billion, the former reality TV star enters primary season charged with 78 felonies in three separate criminal probes.

He is due to go on trial in New York in March next year over allegations that he covered up "hush money" payments to a porn star, and is scheduled to be tried two months later over his alleged mishandling of national security secrets.

He is in court on Thursday for a preliminary hearing over his alleged election interference and is expected to soon be charged by state prosecutors over similar allegations in a separate case focused on the southern state of Georgia.

- 'Ripped off' -

Trump launched Save America after losing the 2020 election to Joe Biden, raising $250 million in two months from supporters asked to contribute to an "election defense fund" to contest the outcome.

Fundraising emails used "dangerous and inflammatory" language stating falsely that donations could help "Stop the Steal," according to a 2022 report by the congressional committee investigating Trump's misconduct around the election.

None of the money went to recount and election-contest related expenses, with much going unspent and significant sums being divided between funding the Republican National Committee and bolstering Trump's political war chest.

"In short, President Trump and his campaign ripped off supporters by raising more than $250 million by claiming they wanted to fight fraud they knew did not exist and to challenge an election they knew he lost," the committee wrote.

His 2023 spending has opened a lane for Florida governor Ron DeSantis, who is running a distant second in Republican primary polling, to question the frontrunner's priorities.

"Trump has spent over $60 million on two things: falsely attacking DeSantis and paying his own legal fees, not a cent on defeating Biden," DeSantis campaign spokesman Andrew Romeo said.

A group of Trump allies led by political advisor Michael Glassner have created the "Patriot Legal Defense Fund" to take on legal bills racked up by Trumpworld figures that are not family members or the former president himself.

The Trump campaign did not respond to a request for comment but it has previously stated that cash used for legal bills was helping "to protect these innocent people from financial ruin and prevent their lives from being completely destroyed."