WASHINGTON — The House committee investigating the Jan. 6 riot at the U.S. Capitol has issued a subpoena to a former Justice Department lawyer who positioned himself as an ally of Donald Trump and aided the Republican president’s efforts to challenge the results of the 2020 election.

Jeffrey Clark Susan Walsh/Associated Press

The subpoena to Jeffrey Clark, revealed Wednesday, came amid signs of a rapidly escalating congressional inquiry. At least three of the people who were involved in organizing and running the rally that preceded the violent riot have handed over documents in response to subpoenas from the committee.

The demands for documents and testimony from Clark reflect the committee’s efforts to probe not only the deadly insurrection but also the tumult that roiled the Justice Department in the weeks leading up to it as Trump and his allies leaned on government lawyers to advance his baseless claims that the election results were fraudulent. Trump loyalists stormed the Capitol in an effort to disrupt the congressional certification of Democrat Joe Biden’s victory.

Clark, an assistant attorney general in the Trump administration, has emerged as a pivotal character in that saga. A Senate committee report issued last week shows how he championed Trump’s efforts to undo the election results inside the Justice Department and clashed as a result with superiors who resisted the pressure, culminating in a dramatic White House meeting at which Trump floated the idea of elevating Clark to attorney general.

“The Select Committee’s investigation has revealed credible evidence that you attempted to involve the Department of Justice in efforts to interrupt the peaceful transfer of power,” the chairman of the committee, Democratic Rep. Bennie Thompson of Mississippi, wrote in a letter to Clark announcing the subpoena.

While Trump ultimately did not appoint Clark acting attorney general, Clark’s “efforts risked involving the Department of Justice in actions that lacked evidentiary foundation and threatened to subvert the rule of law,” Thompson added.

The committee has scheduled a deposition for Oct. 29 and demanded documents by the same date. A lawyer for Clark declined to comment.

The Jan. 6 panel has so far sought testimony from a broad cast of witnesses, but its demands of Trump aides and associates are potentially complicated by Trump’s vow to fight their cooperation on grounds of executive privilege.

Already one witness, Steve Bannon, has told the committee that he will not cooperate based on Trump’s directive, though the committee has said it was “engaging” with two other Trump officials – former White House chief of staff Mark Meadows and former Defense Department official Kashyap Patel. It is also unclear whether Dan Scavino, Trump’s longtime social media director and one of his most loyal aides, will cooperate.

Biden formally rejected Trump’s claim of executive privilege surrounding a tranche of documents requested from the former president’s time in the White House, and set up their potential release to Congress in mid-November. White House counsel Dana Remus wrote to the National Archives in a letter released Wednesday that Biden believes that “an assertion of executive privilege is not in the best interests of the United States.”

Others, though, are cooperating, including some of the 11 who organized or staffed the Trump rally that preceded the riot. They were given a Wednesday deadline to turn over documents and records, and have also been asked to appear at separate depositions the committee has scheduled beginning this month.

Among those responding to the Wednesday deadline was Lyndon Brentnall, whose firm was hired to provide event security that day. “All the documents and communications requested by the subpoena were handed in,” he told the Associated Press.

Brentnall had previously said his firm had “every intention” of complying with the select committee. “As far as we’re concerned, we ran security at a legally permitted event run in conjunction with the U.S. Secret Service and the Park Police,” he said.

Two longtime Trump campaign and White House staffers, Megan Powers and Hannah Salem, who were listed on the Jan 6. rally permit as “operations manager for scheduling and guidance” and “operations manager for logistics and communications,” have also provided documents or are planning to do so.

Powers, who served as the Trump reelection campaign’s director of operations, intends to provide the requested documentation and to meet with the committee – though it remains unclear what form such meetings will take, according to a person familiar with her response who spoke on condition of anonymity.

Many of the rioters who stormed the Capitol on Jan. 6 marched up the National Mall after attending at least part of Trump’s rally, where he had repeated his meritless claims of election fraud and implored the crowd to “fight like hell.”

The results of the election were confirmed by state officials and upheld by the courts. Trump’s own attorney general, William Barr, had said the Justice Department found no evidence of widespread fraud that could have overturned the results.

It remains unclear whether the others who were subpoenaed intend to cooperate. A committee spokesperson declined to comment Wednesday on the responses it had received and how many of the 11 were complying.

Members of the committee, including Wyoming Rep. Liz Cheney, the panel’s Republican vice chairwoman, have threatened to pursue criminal contempt charges against subpoenaed witnesses who refuse to comply. A House vote would send those charges to the Department of Justice, which would then decide whether to prosecute.

The subpoena to Clark follows the release of a Senate Judiciary Committee report that documented extraordinary tensions within the senior ranks of the Justice Department in December and January as Trump and his allies prodded the law enforcement agency to help him in undoing the election.

The report from the committee’s Democratic majority depicts Clark as a relentless advocate inside the building for Trump’s efforts, even presenting colleagues with a draft letter pushing Georgia officials to convene a special legislative session on the election results. Clark wanted the letter sent, but superiors at the Justice Department refused.

“We need to understand Mr. Clark’s role in these efforts at the Justice Department and learn who was involved across the administration,” Thompson wrote.

Two additional organizers, Ali Alexander and Nathan Martin, as well as their “Stop the Steal” organization, were also subpoenaed for documents, which are due Oct. 21.

Alexander wrote in a Telegram post Monday that the committee was “subpoenaing people in bad faith.”

“So maybe this Select Committee is bogus?” he added. “Everyone is waiting to see what I’ll do.”

Colvin reported from New York and Smith from Providence, Rhode Island. Associated Press writers Farnoush Amiri and Zeke Miller in Washington contributed to this report.