Mr. Giuliani claimed fraud at a series of unofficial state legislative hearings, and even argued one election fraud case himself, in federal court in Philadelphia, where he suffered a decisive defeat.
“Voters, not lawyers, choose the president,” the court declared at one point.
On Jan. 6, speaking to a crowd of Trump supporters before the attack on the Capitol, Mr. Giuliani called for “trial by combat.” Later, as the building was under siege, he called lawmakers in an attempt to delay the certification of Joseph R. Biden Jr.’s victory.
“Senator Tuberville, or I should say Coach Tuberville, this is Rudy Giuliani, the president’s lawyer,” Mr. Giuliani said in a voice mail message intended for Senator Tommy Tuberville, Republican of Alabama, but mistakenly left on the phone of Senator Mike Lee, Republican of Utah. “I’m calling you because I want to discuss with you how they’re trying to rush this hearing and how we need you, our Republican friends, to try to just slow it down.”
Ms. Ellis, the committee said, “prepared and circulated” two memos analyzing the constitutional authority for former Vice President Mike Pence to reject or delay counting electoral votes from states where Mr. Trump’s allies had attempted to arrange for the submission of an alternate slate of electors. In the memos, obtained by Politico, Ms. Ellis advised that Mr. Pence had the authority to not count electoral votes from six states in which the Trump campaign falsely alleged there was widespread fraud.
Ms. Powell was among the leading promoters of some of the most far-fetched and fantastical claims of widespread voter fraud, including a bizarre conspiracy theory alleging a vast plot by China, Venezuela and the financier George Soros to hack into Dominion Voting Systems machines to flip votes away from Mr. Trump to Mr. Biden.
She, too, urged Mr. Trump to seize voting machines, according to the committee.
In December, Mr. Trump considered naming Ms. Powell to be a special counsel overseeing an investigation of voter fraud, even after his campaign had sought to distance itself from her as she aired wild and baseless claims about Dominion voting machines.
Her organization, Defending the Republic, raised $14.9 million between December 2020 and July. Ms. Powell’s group has more than $9.3 million in funds on hand, according to an independent audit filed with Florida, which investigated the organization and alleged multiple violations of state law.