Mr. Christie rejoined the campaign trail, energized by a debate performance in which he seized the spotlight with attacks on Mr. Trump and his rivals.Former Gov. Chris Christie of New Jersey returned to New Hampshire on Thursday for a series of campaign appearances that quickly became more like a victory lap after his performance in the third Republican Party debate.In a series of stops at universities, Mr. Christie told war stories about his moments in the debate spotlight, offering a highlights reel of his zingers against his opponents. Mr. Christie, who has faced calls to exit the race from some donors and strategists, won praise for his performance on the stage, particularly his series of scathing attacks against Gov. Ron DeSantis of Florida and Vivek Ramaswamy, a tech entrepreneur.Speaking to students at Keene State College in the western part of the state, Mr. Christie recounted with visible glee a shouting match with Mr. DeSantis, who dodged a question on Mr. Trump’s fitness to be president. Mr. DeSantis, he implied, was eager to quickly move past the question. Mr. Christie said that he wouldn’t allow it.“All he’s looking to do is for the red light in front of us to come on, which means he could stop,” Mr. Christie said, adding, “When the light goes on, he stops and he lets out a sigh of relief, like, Oh my God, thank God it’s over. But it wasn’t, because there’s another living human being onstage. And I said, ‘He doesn’t answer the question.’”Mr. Christie cast the debate as a crucial moment in a race that is heading into the final stages before votes are cast in January. “I’m telling you right now, I’m gonna be the last person standing against Donald Trump,” he said. “There’s gonna be no place for him to hide. And then you’re gonna be more entertained than you’ve ever been in your entire life.”Mr. Christie is widely trailing his rivals, sitting at third place in polls in New Hampshire. He has staked his candidacy on a full-throated attack against Mr. Trump but has struggled to find an audience among Republican primary voters for that message. He seized the opportunity onstage Wednesday, painting Mr. Trump as one step away from being a felon and attacking the other Republican presidential candidates for their reluctance to criticize the former president.In an interview, Mr. Christie said he was personally offended by Mr. Ramaswamy’s attacks on Nikki Haley, a former governor of South Carolina, as being corrupt, unintelligent and inauthentic.“Who would think that somebody would be enough of a jackass to say that Nikki Haley was not as smart as his 3-year-old son,” Mr. Christie said in an interview. “When I heard that, I have to tell you the truth, I was just like, I’m not gonna let him get away with that.”Whether his energetic performance could give Mr. Christie an opportunity to make gains among voters who are most sympathetic to his anti-Trump crusade remains to be seen.Mr. Christie, gesturing below, has trailed his rivals for most of the campaign, and he has been the most vocal critic of former President Donald J. Trump among the Republican field.Sophie Park for The New York TimesAt Franklin Pierce University, Mr. Christie asked for the votes of faculty members and students in attendance — even high schoolers, some too young to cast a ballot in the primary in January.“I urge you to register and get involved. But I’ve got to give you a reason to get involved,” Mr. Christie said.Mr. Christie talked up his policy priorities, including increasing treatment options for people with mental health issues, addressing the opioid epidemic and cutting spending to reduce inflation.Yet, even among a group that tends to tilt Democratic, Mr. Christie faced heckles and criticism. In his appearances, Mr. Christie embraced conservative positions that have not typically energized college students. He did not endorse banning semiautomatic rifles or broadly forgiving student debt. He told a young audience at Keene State College that he is “an unabashed and complete parental rights advocate” when it comes to the issue of transgender youth.As he addressed a packed room in a student hall at Keene State College, protesters outside bearing signs supporting abortion, immigration and Palestine jeered him — dancing, playing music and occasionally banging on the glass windows behind him. One member of the audience tried to use the last question of the town hall to ask why Mr. Christie wears his pants so high.“You know, that’s an example of one of the reasons that political candidates are reluctant at times to come to college campuses,” Mr. Christie said, declining to answer the question.Still, he found some supporters among the packed rooms. Allison Keyson, 19, a student at Keene State College, said she was torn between supporting Mr. Christie and Ms. Haley.“His career is pretty inspiring to me. It’s kind of what I would like to do. I’m gonna get into law, and I would like to go into politics as well,” Ms. Keyson, a registered independent, said. “He is definitely an inspiring candidate.” More