PORTSMOUTH, N.H., FEB. 15 -- Pierre S. (Pete) du Pont IV was having breakfast in a restaurant here and recounted a campaign experience with a sixth-grade class.

"This one boy asked me an extraordinary question for someone that age," he said, shaking his head in admiration. "He asked me how did I deal with rejection."

"I told him, 'The same way you do. You play sports and when you lose one day, you don't quit, you come back and play better tomorrow.' " The front-runners here may experience the exhilaration of success on Tuesday, but others will face the bleak political dawn on Wednesday knowing that they will have to deal with rejection.

Some candidates will head south toward the "Super Tuesday" states being contested March 8, but for the Pete du Ponts of the field, a bottom-of-the-heap finish could mean the end. Others in that situation are Democrats Bruce Babbitt and Gary Hart and Republican Rep. Jack Kemp (N.Y.) -- even though they have vowed to keep up the fight.

They may have to contemplate the prospect of returning to everyday, humdrum life if Tuesday's results spell an end to dreams of leading the western world.

Their attitudes today varied.

In Babbitt, whose campaign in recent days has featured emotional meetings with supporters who are as reluctant as he to see the end of the adventure, the withdrawal symptoms are most painfully evident.

Hart, who dropped out of the race last May after a sex scandal but reentered in December to "let the people decide," is subdued but defiant and determined to press on.

Kemp and du Pont, who were ebullient and optimistic that they will do better than expected despite spotty crowds, also promised to stay in the race. They are struggling with Pat Robertson to finish third here behind Vice President Bush and Sen. Robert J. Dole (R-Kan.).

There was an elegiacal air to Babbitt's campaign today. He finished fifth in Iowa and is sixth here in the latest Washington Post-ABC News poll, leading only Hart.

At an elementary school here, Babbitt read Shel Silverstein's "The Giving Tree" to a first-grade class. When he was finished, one student piped up, "I like you."

"Wow," Babbitt responded, moved. "This is a terrific class."

Afterward, Babbitt mused about his two-year campaign.

"Sometimes it's very tough," he said. "You wake up in another city, another strange motel. My kids I miss very much. My wife I hardly ever see . . . . They bring us together for a conjugal visit, you know, maybe once or twice a month."

But he made it clear that it's worth it.

"I got up after that last debate a couple of days ago and a shiver went down my spine as I looked at the others and said, 'What an extraordinary opportunity to stand here as a candidate for the presidency of the United States of America.' It is not just another horse race, it is being in the middle of a drama . . . that I see being invested with a transcendent importance."

If "harsh realities" force him to withdraw, he said, he might conclude that running for president "is a pursuit where once is truly enough."

On the other hand, he continued, he might find he has fallen victim to "the disease that {Rep. Morris K.} Mo Udall {D-Ariz.} once said can only be cured with embalming fluid."

Hart, campaigning with a tiny entourage and encountering small crowds, vowed to continue his "underdog candidacy" no matter how he fares here.

"This is a marathon," he said. "It is not going to be over tomorrow. It is not going to be over on Super Tuesday. It is not going to be over until the fat lady sings."

He contended that his message would catch on when the voters start deciding which direction they want the country to go.

"What they have to decide is if they want someone to govern this country . . . who is a human being who made a mistake," he said. "I've apologized all over national television and if people aren't accepting of that apology and they want an inferior president, then they can have one."

Rejection and losing were not on the minds of du Pont and Kemp, however.

Kemp's aides said he was closing the gap on Robertson and cautiously predicted that he might finish third. Kemp, however, said he might finish second.

"I'll finish a strong third or higher," Kemp said at an outdoor news conference by the Merrimack River. "I think Bush is falling rapidly."

As a result, Kemp said, the race will come down to him and Dole and Kemp will win the nomination.

"As this race gets turned upside down with a new leader {Dole}, it comes down to the pain and sacrifice and bitter medicine of Bob Dole versus the growth, hope and opportunity progressive conservatism of Jack Kemp," he said. "I'm the one conservative who understands how to bring the Reagan revolution to completion. This is just the beginning."

He accused Bush of being as incurable an advocate of tax increases as Dole.

"I think it's a case of consumer fraud for the vice president to run ads accusing Dole of being a tax increaser when both George Bush and Bob Dole never met a tax increase they didn't like," he said.

Du Pont contended his campaign has begun to move because New Hampshire voters are getting his message of opposing tax increases.

"I think we did extraordinarily well in the debate last night when I shoved that piece of paper in Dole's face and asked him to sign the pledge of no tax increases," du Pont said. "That was a significant moment in this campaign because everyone in New Hampshire knows what taking the pledge means. It means no tax increases, a subject that is near and dear to the hearts of these New England Yankees.

"I think it's possible I could win," he said. "I'm going south from here for Super Tuesday and how well we do there depends on how much oomph we get from here."

Babbitt, at one meeting with his backers -- some of whom committed to him two years ago -- may have spoken for all presidential candidates of all times.

"One more {question} and I'll quit," he said. "I hate to let loose."

Staff writers David S. Broder, Gwen Ifill and Maralee Schwartz contributed to this report.