WASHINGTON — The Democratic chairman of the House Homeland Security committee accused Donald Trump in a federal lawsuit on Tuesday of inciting the deadly insurrection at the U.S. Capitol and of conspiring with his lawyer and extremist groups to try to prevent Congress from certifying the results of the presidential election he lost to Joe Biden.

The lawsuit from Mississippi’s Rep. Bennie Thompson is part of an expected wave of litigation over the Jan. 6 riot and is believed to be the first filed by a member of Congress. It seeks unspecified punitive and compensatory damages.

The case also names as defendants the Republican former president’s personal lawyer Rudy Giuliani and groups including the Proud Boys and the Oath Keepers, extremist organizations that had members charged by the Justice Department with taking part in the siege.

A Trump adviser, Jason Miller, said in a statement Tuesday that Trump did not organize the rally that preceded the riot and “did not incite or conspire to incite any violence at the Capitol on Jan. 6th.” A lawyer for Giuliani did not immediately return an email seeking comment.

The suit, filed in federal court in Washington under a Reconstruction-era law known as the Ku Klux Klan Act, comes three days after Trump was acquitted in a Senate impeachment trial that centered on allegations that he incited the riot, in which five people died. That acquittal is likely to open the door to fresh legal scrutiny over Trump’s actions before and during the siege. Additional suits could be brought by other members of Congress or by law enforcement officers injured while responding to the riot.

Even some Republicans who voted to acquit Trump on Saturday acknowledged that the more proper venue to deal with Trump was in the courts, especially now that he has left the White House and lost certain legal protections that shielded him as president.

The suit traces the drawn-out effort by Trump and Giuliani to cast doubt on the election results even though courts across the country, and state election officials, repeatedly rejected their baseless allegations of fraud. Despite evidence to the contrary, the suit says, the men portrayed the election as stolen while Trump “endorsed rather than discouraged” threats of violence from his angry supporters in the weeks leading up to the assault on the Capitol.

“The carefully orchestrated series of events that unfolded at the Save America rally and the storming of the Capitol was no accident or coincidence,” the suit says. “It was the intended and foreseeable culmination of a carefully coordinated campaign to interfere with the legal process required to confirm the tally of votes cast in the Electoral College.”

Presidents are historically afforded broad immunity from lawsuits for actions they take in their role as commander in chief. But the lawsuit filed Tuesday was brought against Trump in his personal, not official, capacity and alleges that none of the behavior at issue had to do with his responsibilities as president.

“Inciting a riot, or attempting to interfere with the congressional efforts to ratify the results of the election that are commended by the Constitution, could not conceivably be within the scope of ordinary responsibilities of the president,” Joseph Sellers, a lawyer for Thompson, said in an interview.

“In this respect, because of his conduct, he is just like any other private citizen,” he said.

Sellers, a lawyer with the Washington law firm of Cohen Milstein, filed the case along with the NAACP. Several other members of Congress are expected to join.