According to widespread media reports, Waldron said he had briefed members of Congress on a PowerPoint presentation listing proposals for how to challenge Trump's defeat by President Joe Biden in the 2020 presidential election.
"Mr Waldron reportedly played a role in promoting claims of election fraud and circulating potential strategies for challenging results of the 2020 election. He was also apparently in communication with officials in the Trump White House and in Congress discussing his theories in the weeks leading up to the January 6th attack," Representative Bennie Thompson, who chairs the select committee, said on Thursday.
The options in the PowerPoint presentation, which was handed over to the January 6 Select Committee by former Trump chief of staff Mark Meadows, included declaring a national security emergency and seizing paper ballots.
"The document he reportedly provided to administration officials and members of Congress is an alarming blueprint for overturning a nationwide election," Thompson said.
The committee has issued more than 50 subpoenas and heard from more than 300 witnesses in its investigation of the attack by supporters of the Republican ex-president as Congress met to formally certify his loss to Democrat Biden.
Four people died the day of the riot, and one Capitol police officer died the next day of injuries sustained while defending Congress. Hundreds of police were injured during the multi-hour onslaught, and four officers have since taken their own lives.
In its letter to Waldron, the committee says that, according to public reporting, he claimed to have visited the White House on multiple occasions after the November 2020 election and spoke to Meadows "maybe 8 to 10 times" and briefed several members of Congress on election fraud theories.
Waldron did not immediately respond to a text message seeking comment.
The panel has begun contempt of Congress proceedings against three Trump supporters for failure to comply with its subpoenas - Meadows, former Trump chief strategist Steve Bannon, and Jeffrey Clark, a former Trump Justice Department official.
Trump has urged associates not to co-operate, calling the Democratic-led investigation politically motivated and arguing that his communications are protected by executive privilege.Â
Courts have rejected that argument.
