"Four years ago, we sent Donald J. Trump, an outsider and businessman, to Washington to shake things up. And he did. We need to protect his victories."
Lawmakers on the Republican right flank are aiming to remove Cheney, the daughter of former Vice President Dick Cheney, as the party's No. 3 in the House.
"We request the opportunity to meet with you to discuss our proposal in greater detail and how we can work together to meet the needs of the American people."
Portman, a moderate Republican who had urged former President Donald Trump to denounce the violence of his supporters, announced on Monday he would not be seeking reelection for his seat.