Nikki Haley did well enough in the Iowa caucuses Monday night to keep her supporters’ hopes alive. But her third-place showing, on the heels of Ron DeSantis and a mile behind Donald Trump, was also just disappointing enough to raise doubts about her candidacy.

Her plan coming out of Iowa is a classic underdog strategy: Use strong early results to upend expectations in the contests to come, reshaping the dynamic of the race one upset victory at a time. So, the thinking goes, her solid-enough performance in Iowa will propel her higher in New Hampshire, where she holds a strong second place in the polls.

It’s possible. But even if Ms. Haley does well in New Hampshire, it won’t matter. That’s because Ms. Haley is starkly out of step with the evolution of her party over the past decade.

The shape of today’s Republican electorate can be seen most clearly in national polling of Republican voters, where Mr. Trump has led by a substantial margin for months. Even in the unlikely event that all the voters who have told pollsters in recent weeks that they support Mr. DeSantis, Chris Christie and the former Arkansas governor Asa Hutchinson switched over to Ms. Haley, she would reach only the high 20s, placing her more than 30 points behind Mr. Trump, who sits at around 60 percent. (The voters who have said they support Vivek Ramaswamy, who dropped out of the race on Monday night, would likely switch to Mr. Trump.)