“It was cathartic as hell,” said Amanda Litman, executive director of Run for Something, which supports young Democrats running for office. “This felt like if you’re going to count her out, she’s not going down without a fight.”

Now, with another debate happening Tuesday night and the South Carolina primary just four days away, Ms. Warren’s supporters are waiting to see if she can do it again.

If last week’s debate did move the needle, it wasn’t clear in her fourth-place finish in Nevada. The state held its early caucus voting, in which about 75,000 of the 105,000 total votes were cast, before the debate, meaning any potential bounce for Ms. Warren was not fully reflected.

And Ms. Warren has had strong debate performances before, of course — especially last summer and early in the fall, when she was surging in the polls and her path to the nomination was easier to imagine.

But this one was different, precisely because that path has become so much less clear.

“It was the woman of a year ago,” Kelsey Duckett, 35, said at a Warren rally in Denver on Sunday. “She’s showing us why we supported her in the beginning.”