Liz Cheney is not campaigning to hold on to her leadership post.

The last time Representative Liz Cheney of Wyoming was staring down an attempt to purge her from House Republican leadership, as punishment for having voted to impeach former President Donald J. Trump, she whipped the vote herself, privately calling almost every member of her party to lock up support until she was confident the challenge would fail.

But three months later, as she prepares to face a fresh vote on Wednesday to force her out of the No. 3 leadership post — this one orchestrated by party leaders who have grown exasperated with her outspoken repudiation of Mr. Trump’s election lies — Ms. Cheney has no such illusions of hanging on.

On the precipice of what looks to be an almost certain ouster, rather than barreling through her Rolodex of lawmakers or rallying her extensive network of backers off Capitol Hill to try to cling to her job, Ms. Cheney has defiantly embraced her downfall, offering herself as a cautionary tale in what she is portraying as a battle for the soul of the G.O.P.

As a replacement for the Wyoming Republican, leaders have united behind Representative Elise Stefanik of New York, a onetime moderate whose fealty to Mr. Trump and backing for his false narrative of a stolen election have earned her broad support from the party’s rank-and-file that Ms. Cheney, as a lifelong conservative, no longer commands.

Ms. Cheney has repeatedly warned that trying to avoid talking about the Jan. 6 attack on the Capitol and Mr. Trump’s false election claims will not only further alienate would-be Republican voters, but also cause “profound long-term damage” to the country. A former State Department official, she has invoked the parallels between what unfolded on Jan. 6 and her work in authoritarian countries to explain why she was so determined to publicly condemn the attempted insurrection.