The first caucus, in Iowa, is in a state Trump can’t count on winning. Trump lost the Iowa caucuses in 2016. Trump’s trade wars have been particularly hard on the American farm belt. Trump’s bombastic personality isn’t stylistically well suited to Iowa. And while Trump still does well in top-line Iowa poll numbers, a near-plurality of Iowans have said for a while they hope a serious challenger to Trump emerges.
Iowa’s Republican senior statesman, revered U.S. Sen. Chuck Grassley, will be 89 years old by Election Day of 2022, when his current term runs out. It is quite likely he will retire. He therefore would be free, without fear of personal electoral repercussions, to do the right thing and endorse Haley against Trump. If he does, and if he effectively turns over his organization to her, she could well win the caucuses.
Bloodied by that defeat, Trump would no longer look like such a tough guy. As his whole persona depends on him appearing (to many) to be the strongest guy around, a setback like this would be even more harmful to him than to most incumbents.