A pop psychologist might say that Mrs. Clinton was showing symptoms of denial or of being divorced from reality, but she has said for months that she will not quit as long as there remains a mathematical possibility that she could capture the nomination. That chance narrowed considerably Tuesday night, but the path is not totally blocked.

As a brief news conference after her remarks at the college, she said, “It’s a new day, it’s a new state, it’s a new election,” her upbeat tone never wavering. “I’m staying in this race until there’s a nominee. I’m going to work as hard as I can to become that nominee.”

Jay Carson, a campaign spokesman, said that he had spoken privately with Mrs. Clinton on Wednesday morning and that she was in a good mood.

“We feel we did well last night,” Mr. Carson said. “She is not someone who is buffeted by the day-to-day ups and downs of the campaign. She is tough and tenacious. That’s why she’s a phenomenal campaigner and why she’d be a great president.”

“She’s unflappable,” he added. “She’s proven that to you in the press and to the voters.”

In her victory speech in Indianapolis on Tuesday night (in which she also conceded North Carolina), Mrs. Clinton vowed to press on but sounded wistful at times about a long campaign that many believe will soon draw to an end. She delivered an unusually long list of thank-yous, reminded Democrats that “we are all on the same team” and pledged to support the nominee  if she does not prevail.

But there was no sense of leave-taking Wednesday, as Mrs. Clinton began what she described in a fund-raising letter as the “final 28 days of voting.” But her supporters sensed that more than a calendar page was turning. Many said they felt that Mrs. Clinton’s quest was coming to a close.