Doug Mastriano, Pa. GOP nominee for governor, cooperating with Jan. 6 panel

Doug Mastriano, the Republican nominee for governor of Pennsylvania, has provided documents to the House committee investigating the Jan. 6 attack on the U.S. Capitol and has agreed to sit for a voluntary interview, his attorney confirmed.

"We provided everything we found that was not part of his legislative functions," Mastriano's lawyer, Tim Parlatore, told NBC News. "My client has nothing to hide."

Parlatore said the interview has yet to be scheduled. Mastriano’s cooperation with the committee investigating the Capitol riot was first reported by Politico.

Mastriano, a state senator, responded Tuesday to a subpoena the committee issued in February, which sought information related to his role in an effort to send so-called alternate electors for then-President Donald Trump to Congress after his loss in the 2020 election.

Mastriano responded with a letter from his lawyer that linked to "certain documents and communications in his possession, custody, or control." Most of the documents he provided were public social media posts and correspondence; the batch did include receipts and a passenger list from buses carrying pro-Trump protesters to Washington on Jan. 6, 2021, that Mastriano's campaign had paid for and organized.

Mastriano also provided letters he sent urging lawmakers and the Justice Department to back Trump's efforts to overturn the election or halt its ascertainment in Congress on Jan. 6.

In February, Rep. Bennie Thompson, D-Miss., the chairman of the committee, wrote to Mastriano that the panel was aware that he has "knowledge of and participated in a plan to arrange for an alternate slate of electors to be presented to the president of the Senate on January 6, 2021, and we understand that you spoke with former President Trump about your post-election activities.”

"Based on your public statements, we understand that you were present during the attack on the U.S. Capitol on January 6, 2021, and that you witnessed 'agitators ... getting in the face of the police' and 'agitators ... start pushing the police up the [Capitol] steps,'" Thompson wrote.

Mastriano, who has campaigned at events alongside QAnon adherents, was on restricted Capitol grounds on Jan. 6, just feet from rioters breaching police barricades. He has said he left before the riot.

Mastriano, who won the mid-May primary for governor by more than 23 percentage points, built his brand and loyal following by doggedly seeking to overturn President Joe Biden’s win in Pennsylvania, a critical presidential battleground. Just days before the election, with his lead growing in the polls, Mastriano was endorsed by Trump, even though other Republicans in the state felt he presented the party's worst chance to beat state Attorney General Josh Shapiro, the Democratic nominee for governor, in the general election.

Whoever wins the election this fall will play a huge role in oversight of the 2024 presidential election in Pennsylvania, as the governor appoints the secretary of state. Just last week, Mastriano was raising money off false stolen election claims, writing in a fundraising appeal that 2020 "marked the first time American's voices were not heard."