As recently as this summer, a poll with Donald J. Trump leading among young voters would have been eye-popping. Now, it’s increasingly familiar — and our new New York Times/Siena College national survey released Tuesday morning is no exception. For the first time, Trump leads President…

In the half century of modern presidential primaries, no candidate who led his or her nearest rival by at least 20 points at this stage has ever lost a party nomination. Today, Donald J. Trump’s lead over Ron DeSantis is nearly twice as large: 37 points, according to a New York Times/Siena…