Looking at who supporters of the other candidates name as their second choice also helps explain why Trump’s support doesn’t collapse when the field narrows. While Rubio voters tend to choose Cruz as their second choice, and John Kasich voters choose Rubio, many Cruz and Carson voters say their second choice is Trump. It’s the same in state polls. A new poll in North Carolina, for instance, finds that both Cruz and Carson voters pick Trump as their next favorite. Rubio voters choose Cruz but still prefer Trump to Kasich. Most remarkably of all, Trump almost ties Rubio among former supporters of Jeb Bush.

Trump’s not doomed in a two-way race because he’s not a niche candidate. In New Hampshire, he won women and men, young and old, college graduates and noncollege graduates, rich and poor, conservatives and moderates. In South Carolina, he narrowly lost college graduates and voters who called themselves “very conservative.” But he still won among voters of every age, income level, gender, and issue concern. His support was similarly broad-based in Nevada.

Republican voters also agree with Trump on many of his signature issues. Almost three-quarters want the United States to build a wall along its southern border. Almost 60 percent support a ban on Muslim immigration. (Among GOP voters in New Hampshire and South Carolina, the figure was even higher.) A plurality opposes the Trans-Pacific Partnership trade agreement. Most believe America’s campaign-finance system is corrupt.