‘We have to have hope, right?’ Democrats grasp for momentum.

For the past three years, Democrats have drawn fuel from a collective sense of outrage. But as New Hampshire prepares to register its choice for the Democratic nominee on Tuesday, there are signs that some of that anger may be fading into something more like weary resignation.

“So many people, myself included, have gotten to the point where it’s like, ‘Trump did this!’ and I’m just like, ‘Yeah, whatever,’” says Emily Hay, an energy efficiency coordinator from Tilton, New Hampshire.

Last week, in particular, was a kind of dispiriting...