MANCHESTER, N.H. — President Trump spoke for an hour to an enthusiastic crowd of more than 11,000 at the Southern New Hampshire University Arena on Monday night under banners that read “Promises Made” and “Promises Kept.” Two nights earlier, this same venue hosted the New Hampshire Democratic Party’s 100 Club dinner.

“We have more in this arena than all the other candidates in the Democratic Party,” Mr. Trump said. “One candidate today had 104 people.”

The crowd laughed.

“I see them campaigning down the street. It’s really boring stuff,” Mr. Trump added. “We are going to defeat the radical, socialist democrats. We are going to win New Hampshire in a landslide.”