ORLANDO, Fla. — House Republicans on Monday rallied around former President Donald Trump ahead of his expected indictment by a Manhattan grand jury, using their investigative power to scrutinize active criminal inquiries targeting him as at least one other GOP lawmaker endorsed his 2024 presidential campaign.

Three Republican committee chairmen demanded Monday that Alvin Bragg, the Manhattan district attorney who is said to be close to indicting Trump, provide communications, documents and testimony about his investigation, an extraordinary move by Congress to involve itself in an active criminal inquiry.

“You are reportedly about to engage in an unprecedented abuse of prosecutorial authority,” wrote Reps. Jim Jordan of Ohio of the Judiciary Committee, James Comer of Kentucky of the Oversight and Accountability Committee and Bryan Steil of Wisconsin of the Administration Committee. “If these reports are accurate, your actions will erode the confidence in the evenhanded application of justice and unalterably interfere in the course of the 2024 presidential election.”

They demanded “all documents and communications referring or relating to the New York County District Attorney Office’s receipt and use of federal funds.”

That office receives little funding from the federal government, according to its most recent budget, but the letter also served as a warning to the FBI and the Justice Department, which is also considering prosecutions of Trump.

The letter was House Republicans’ latest effort to use their investigatory powers to defend Trump. They have authorized a new subcommittee to scrutinize criminal investigations into Trump’s conduct and quietly wound down a congressional inquiry into his finances and conflicts of interest as president. The Justice Department has resisted what federal prosecutors view as unnecessary intrusions into their work, citing longstanding department policy. Bragg was anticipated to be unlikely to allow Republicans access to materials related to an active case.

Trump’s call for protest demonstrations should he be indicted, however, have generated mostly muted reactions from supporters, with even some of his most ardent loyalists dismissing the idea as a waste of time or a law enforcement trap.

Still, Trump’s lawyers have quietly urged the Republican-led House to interfere.

Last month, Trump’s lawyer Joseph Tacopina wrote to Jordan calling on Congress to investigate the “egregious abuse of power” by what he called a “rogue local district attorney,” according to a copy of the letter obtained by The New York Times.

Rep. Anna Paulina Luna of Florida, who has been loyal to Trump and Gov. Ron DeSantis of Florida, on Monday announced her official endorsement of Trump’s presidential campaign, indicating that the expected indictment had pushed her to unequivocally choose sides.

“I support President Trump,” Luna said in a statement to The New York Times. In explaining her support, she said that Bragg was “trying to cook up charges outside of the statute of limitation against Trump” and that “this is unheard-of, and Americans should see it for what it is: an abuse of power and fascist overreach of the justice system.”

Speaker Kevin McCarthy, R-Calif., also said Sunday that Bragg was politically motivated but argued against protests. “It’s interesting to me that he spent his whole time as a DA lowering felonies not to prosecute,” McCarthy said of Bragg. “Republicans and Democrats alike hate this kind of justice.”

The ambivalence about protest marches raises questions about whether Trump, though a leading GOP contender in the 2024 presidential race who retains a devoted following, still has the power to mobilize loyalists the way he did more than two years ago before the Jan. 6, 2021, insurrection at the U.S. Capitol. It also suggests that the hundreds of arrests that followed the Capitol riot, not to mention the convictions, may have dampened the desire for repeat mass unrest.

Still, law enforcement is continuing to monitor online chatter warning of protests and violence if Trump is arrested, with threats varying in specificity and credibility, officials told The Associated Press.

Around the time the Manhattan courthouse complex opened Monday, a New York Police Department truck began dropping off portable metal barricades that could be used to block off streets or sidewalks.

Associated Press contributed.