WASHINGTON (NewsNation Now) — A Democratic congressman accused former President Donald Trump in a federal lawsuit Tuesday of inciting the deadly insurrection at the U.S. Capitol and of conspiring with his lawyer and extremist groups to try to prevent the Senate’s certification of Joe Biden’s presidential election victory.

The lawsuit from Mississippi’s Rep. Bennie Thompson, chairman of the House Homeland Security Committee, 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 has had members charged by the Justice Department with taking part in the siege.

Lawyers for Trump have denied that he incited the riot. 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 deadly riot. That acquittal is likely to open the door to fresh legal scrutiny over Trump’s actions before and during the siege.

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.

“There’s no doubt that he bears some responsibility,” Republican Sen. Marco Rubio, of Florida, said of Trump during last week’s trial. “If someone thinks he committed a crime then they need to go to the U.S. Attorney’s Office and make that argument.”

The suit traces efforts by Trump and Giuliani to cast doubt on the election results even though courts across the country, and state election officials, repeatedly rejected their unfounded 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 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.”

During the impeachment, Trump’s lawyers argued that the president’s words weren’t intended to incite violent and that the trial was noting but a “witch hunt” designed to prevent him from serving office again.

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 Washington lawyer who along with the NAACP filed the lawsuit on Thompson’s behalf, said in an interview.

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

Though the impeachment case focused squarely on accusations of incitement, the lawsuit more broadly accuses Trump of conspiring to disrupt the constitutional activities of Congress – namely, the certification of election results establishing Biden’s victory – through a monthslong effort to discredit the outcome and to lean on individual states and his own vice president to overturn the contest.

The case against Trump was brought under a provision of the Ku Klux Klan Act of 1871, which was passed in response to KKK violence and prohibits violence or intimidation meant to prevent Congress or other federal officials from carrying out their constitutional duties.

“Fortunately, this hasn’t been used very much,” Sellers said. “But what we see here is so unprecedented that it’s really reminiscent of what gave rise to the enactment of this legislation right after the Civil War.”

At a press briefing Tuesday, White House press secretary Jen Psaki briefly commented on Biden’s response to the lawsuit.

“He certainly supports the rights of individuals, members of Congress and otherwise, to take steps through the judicial process,” Psaki said.

The lawsuit was filed a day after House Speaker Nancy Pelosi announced that Congress will establish an independent, Sept. 11-style commission to look into the deadly insurrection at the Capitol.

Psaki said Biden would support the establishment of such a commission.

“It’s certainly one the president would support,” Psaki said. “He supports efforts to move forward with it.”

“We’re doing something new here and there’s going to be an independent Justice Department to determine what any path forward in any investigation would look like,” Psaki said.

Lawmakers from both parties have signaled that more inquiries are likely.

“There should be a complete investigation about what happened,” said Louisiana Sen. Bill Cassidy, one of seven Republicans who voted to convict Trump. “What was known, who knew it and when they knew, all that, because that builds the basis so this never happens again.”

Read the full lawsuit:

The Associated Press contributed to this report. Reporting by Eric Tucker.