The Republican National Committee has agreed to cover up to $1.6 million of Donald J. Trump’s personal legal bills, according to a person familiar with the matter, in an unusual arrangement under which the party is paying to defend the former president from ongoing investigations that focus on his private business practices.

The first payments, for $121,670, were made in October to the firm of Mr. Trump’s lawyer Ronald P. Fischetti, and were publicly reported last month to the Federal Election Commission.

The decision by the Republican Party to cover up to $1.6 million in legal fees was first reported on Thursday by The Washington Post and was confirmed by the person familiar with the matter, who spoke on the condition of anonymity to discuss private negotiations.

Emma Vaughn, an R.N.C. spokeswoman, said in a statement that the party’s executive committee had approved “paying for certain legal expenses” related to Mr. Trump.

“As a leader of our party, defending President Trump and his record of achievement is critical to the G.O.P.,” she said. “It is entirely appropriate for the R.N.C. to continue assisting in fighting back against the Democrats’ never-ending witch hunt and attacks on him.”

Mr. Fischetti is representing Mr. Trump as prosecutors in Manhattan weigh the possibility of charging him with fraud. At issue is whether he inflated the value of his assets to defraud lenders, according to people familiar with the investigation. The office of the Manhattan district attorney, Cyrus R. Vance Jr., has questioned one of Mr. Trump’s accountants before a grand jury in recent weeks.

In a parallel civil fraud investigation, the New York State attorney general, Letitia James, whose office is also involved in the criminal inquiry, is seeking to question Mr. Trump under oath. The former president has accused both investigations of being politically motivated, and many Republican leaders have echoed his arguments.

“Letitia James wants to politically weaponize her position as Attorney General instead of exemplifying impartiality and protecting the interests of all New Yorkers,” Mr. Trump said in a statement on Wednesday.

A spokesperson for Mr. Trump did not immediately respond to a request for comment. Mr. Fischetti declined to comment. The Republican National Committee will disclose its November spending, including any lawyer fees for Mr. Trump, by Dec. 20.

Stephen Gillers, a law professor at New York University and an expert on legal ethics, said that the payments did not necessarily raise any ethical problem from a legal perspective, as long as the party neither influenced Mr. Trump’s lawyers in any way nor gained access to confidential information that might arise in the course of the investigations.

But the payments showed Mr. Trump’s enduring hold on the party he led for four years in the White House. The party continues to lean heavily on his name and popularity in its online fund-raising appeals. He is a lure for major donors as well, and headlined the National Republican Congressional Committee’s fall fund-raiser last month in Florida.

Adonna Biel, a spokeswoman for the Democratic National Committee, said that “if we were the R.N.C.’s donors, we would certainly be asking questions.”

In the past, several of Mr. Trump’s lawyers have clashed with him over their legal fees. In 2019, his former personal lawyer Michael D. Cohen sued the Trump Organization, Mr. Trump’s family business, saying that the company had not fulfilled an agreement to cover its legal costs. In May, The New York Times reported that another lawyer, Rudolph W. Giuliani, had been pressing aides to the former president to pay him for his attempts to overturn the results of the 2020 election.

Michael Levenson contributed reporting.