The N.A.A.C.P. on Tuesday morning filed a federal lawsuit against former President Donald J. Trump and his personal lawyer Rudolph W. Giuliani, claiming that they violated a 19th century statute when they tried to prevent the certification of the election on Jan. 6.
The civil rights organization brought the suit on behalf of Representative Bennie Thompson, Democrat of Mississippi. Other Democrats in Congress — including Representatives Hank Johnson of Georgia and Bonnie Watson Coleman of New Jersey — are expected to join as plaintiffs in the coming weeks, according to the N.A.A.C.P.
The lawsuit contends that Mr. Trump and Mr. Giuliani violated the Ku Klux Klan Act, an 1871 statute that includes protections against violent conspiracies that interfered with Congress’s constitutional duties; the suit also names the Proud Boys, the far-right nationalist group, and the Oath Keepers militia group. The legal action accuses Mr. Trump, Mr. Giuliani and the two groups of conspiring to incite a violent riot at the Capitol, with the goal of preventing Congress from certifying the election.
The suit is the latest legal problem for Mr. Trump: New York prosecutors are investigating his financial dealings; New York’s attorney general is pursuing a civil investigation into whether Mr. Trump’s company misstated assets to get bank loans and tax benefits; and a Georgia district attorney is examining his election interference effort there.