In a flurry of appearances and commentary, former Representative Liz Cheney has stepped up her denunciations of former President Donald J. Trump in a last-ditch effort to persuade Republicans not to nominate him again.
“Tell the world who we are with your vote. Tell them that we are a good and a great nation,” Ms. Cheney told primary voters in New Hampshire on Friday, in a speech at Dartmouth College’s Democracy Summit. “Show the world that we will defeat the plague of cowardice sweeping through the Republican Party.”
A day later, she blasted Mr. Trump’s suggestion on the campaign trail that the Civil War could have been prevented if President Abraham Lincoln had “negotiated.”
“Which part of the Civil War ‘could have been negotiated’? The slavery part? The secession part? Whether Lincoln should have preserved the Union?” she wrote on X. “Question for members of the G.O.P. — the party of Lincoln — who have endorsed Donald Trump: How can you possibly defend this?”
And in an interview on Sunday on “Face the Nation” on CBS News, she denounced Mr. Trump’s attempts to end or delay his criminal trials by arguing that he had immunity against charges related to anything he did in office. She endorsed efforts to remove him from ballots under Section 3 of the 14th Amendment.
“I certainly believe that Donald Trump’s behavior rose to that level,” she said, referring to Section 3’s disqualification of people who engaged in insurrection against the Constitution after taking an oath to support it. (She made a similar comment at Dartmouth, saying, “There’s no question in my mind that his actions clearly constituted an offense that is within the language of the 14th Amendment.”)
“I think that there’s no basis for an assertion that the president of the United States is completely immune from criminal prosecution for acts in office,” she added of Mr. Trump’s appeals on that front. “He’s trying to delay his trial because he doesn’t want people to see the witnesses who will testify against him,” she continued.
A spokesman for Mr. Trump did not respond to a request for comment on Sunday.
Ms. Cheney turned against Mr. Trump in response to the Jan. 6, 2021, attack on the Capitol. As a member of the House, she was one of 10 Republicans who voted to impeach him and one of two who served on the committee that investigated the attack. She lost her Republican primary overwhelmingly in 2022.
Of all the states holding early primaries and caucuses, New Hampshire — where Ms. Cheney spoke on Friday — is the most fertile ground for Trump opponents, thanks to its voters’ moderate tendencies and the fact that independents can vote in the Republican race. Mr. Trump leads his nearest challenger there, Nikki Haley, by about 13 percentage points — a large margin, but substantially smaller than the roughly 30 points by which he leads Ron DeSantis in Iowa and Ms. Haley in South Carolina.
Voting will begin in just one week, when Iowa Republicans hold their caucuses on Jan. 15. The New Hampshire primary comes next, on Jan. 23, followed by Nevada and South Carolina in February.
Ms. Cheney told the audience at Dartmouth that her own plans depended on whether Republican voters heeded her call.
As she has done on several occasions, she left open the possibility of running as a third-party candidate if they nominate Mr. Trump. But at the same time, she indicated a preference for President Biden over Mr. Trump, saying that while she disagreed with Mr. Biden on policy matters, “Our nation can survive and recover from policy mistakes. We cannot recover from a president willing to torch the Constitution.”
“I’m going to do whatever the most effective thing is to ensure that Donald Trump is not elected,” she added. “I’ll make a decision about what that is in the coming months as we see what happens in the Republican primaries.”
A spokesman for Ms. Cheney did not respond to a message asking whether she planned to make an endorsement in the primaries.
