Senator Mitt Romney of Utah said on Tuesday that he believed Donald J. Trump would win the Republican nomination for president if he ran for his former office in 2024, another indication of Mr. Trump’s perceived strength in the party.

“I don’t know if he’ll run in 2024 or not, but if he does, I’m pretty sure he will win the nomination,” Mr. Romney said at the DealBook DC Policy Project.

Mr. Romney noted that “a lot can happen between now and 2024,” but he added, “I look at the polls, and the polls show that among the names being floated as potential contenders in 2024, if you put President Trump in there among Republicans, he wins in a landslide.”

Mr. Romney, the Republican presidential nominee in 2012, is the sole Republican senator who voted to convict Mr. Trump at both of his impeachment trials.

Asked by The New York Times’s Andrew Ross Sorkin whether he would campaign against Mr. Trump, Mr. Romney responded: “I would not be voting for President Trump again. I haven’t voted for him in the past. And I would probably be getting behind somebody who I thought more represented the tiny wing of the Republican Party that I represent.”

Mr. Romney’s comments were a clear sign of Mr. Trump’s enduring position in the Republican Party, even after his election defeat last year and his impeachment on a charge of inciting the assault on the Capitol on Jan. 6.

“He has by far the largest voice and a big impact in my party,” Mr. Romney said.