Liz Cheney warned members of her party that they should stop supporting Donald Trump.
"I say to my Republican colleagues who are defending the indefensible: there will come a day when Donald Trump is gone, but your honor will stay," Cheney said during the panel's first hearing.
She has been ostracized by fellow Republicans over her criticism of Trump after the Capitol attack. She voted for Trump to be impeached on the charge of inciting insurrection. Cheney was removed from her GOP leadership position.
Cheney is one of a number of high-profile Republicans who have spoken out against Trump. She is one of two Republicans who sit on the panel.
The committee is going to hold a number of hearings this month to show how Trump oversaw an effort to overturn the election and stay in power.
In an effort to oust the incumbent lawmaker from Congress, Trump has endorsed the primary challenger of Cheney's opponent. In the August 16 primary, Cheney is trying to keep her seat.