Chris Christie, the former governor of New Jersey, has traveled the world in his quest to stop Donald J. Trump’s march to the Republican nomination. In New Hampshire living rooms as well as the charred homes of Israeli families killed by Hamas, he has assailed the former president as being unfit to lead, antidemocratic and an aspiring dictator.

But now, six months into Mr. Christie’s presidential primary bid, Republicans who share his goal of defeating Mr. Trump are suggesting an entirely different approach for the long-shot candidate.

Quitting.

Republican donors, strategists and pundits are publicly pressuring Mr. Christie to follow the lead of Tim Scott and Mike Pence and formally end his campaign. Many would like him to throw his support behind Nikki Haley, the former South Carolina governor who has risen in the polls in early-voting states in recent weeks.

The focus on Mr. Christie’s bid reflects the anxiety that has consumed anti-Trump Republicans as the race moves into the final weeks before the Iowa caucuses on Jan. 15. Despite three debates, tens of millions of dollars and many months of campaigning, none of the six candidates still challenging Mr. Trump have made much of a dent in his double-digit lead. And they are rapidly running out of time.

“The people who are supporting Chris are not supporting him because they love Chris Christie — they want someone to take on Trump,” said Rick Santorum, the former Pennsylvania senator who dropped out of the presidential race in 2012 after failing to gain enough traction to win the nomination. “He has a really important decision to make as to whether to back out and let his votes go to somebody else, or whether he’s going to actually improve Trump’s chances by staying in.”

But the dynamic this year reminds other Republicans of 2016, when Mr. Trump benefited from the large field, allowing him to divide the voters who preferred other candidates. Mr. Christie remained in that race until he finished sixth in the New Hampshire primary. He endorsed Mr. Trump 17 days later.

“Time is a flat circle, and everyone insists we relive, beat for beat, the 2016 election,” said Sarah Longwell, a Republican strategist who has spent years working to defeat Mr. Trump. “The main thing that Christie could do to make a difference this time is to drop out.”

Mr. Christie views that race differently, saying the candidates running against Mr. Trump — including himself — failed to take the threat of his candidacy seriously enough.

“We all thought, ‘well, at some point he’ll drop out or at some point fade away.’ And we all waited. Hope is not a strategy,” he said, in an interview on Fox News on Monday. “If you want to beat someone, you need to go out and tell people why he’s not right for the job and why you are.”

Yet in a race in which Mr. Trump has maintained an expansive lead, Mr. Christie’s small foothold on the New Hampshire electorate may not make that great a difference.

Patrick Murray, a New Jersey pollster who is the director of the Monmouth University Polling Institute, said his data indicated that only about half of Mr. Christie’s support in New Hampshire would go to Ms. Haley, while the rest would be distributed among the other candidates. The five or six points that Ms. Haley would earn would not be enough for her to come close to Mr. Trump, who leads New Hampshire by nearly 30 points.

“It would help her be a closer second-place finisher,” Mr. Murray said. “It’s just not big enough to make the difference.”

Surrogates for Ms. Haley have been more hesitant to call on Mr. Christie to drop out. Katon Dawson, a former chairman of the South Carolina Republican Party who now serves as an adviser to the Haley campaign in the state, said that decision would be solely “up to Chris Christie.”

“We can’t control what Chris Christie does after New Hampshire or before New Hampshire,” he said. “We can’t control what Ron DeSantis does. All we can do is watch who is raising the money and Nikki Haley is raising money.”

Don Bolduc, a retired Army general who unsuccessfully ran for the Senate in 2022 and has warmed up crowds for Ms. Haley at town halls in New Hampshire, was more blunt when posed the question. “I think it’s time for all of them to drop out and just let Nikki have the passing lane and just go right into the presidency,” he said.

Mr. Christie’s advisers argue that he is playing an important role by being the only candidate willing to take direct and frequent shots at Mr. Trump. Mike DuHaime, one of Mr. Christie’s top strategists, said a case could be made for any of the candidates other than Mr. Trump to drop out, given that none have been able to break the 20 percent mark in polling.

“Whatever case people make to you about Christie, the other two have no path either,” Mr. DuHaime said, referring to Ms. Haley and Gov. Ron DeSantis of Florida. “Should everybody just drop out, or should we try to beat the guy?”

Mr. Christie has run a relatively low-budget campaign, powered by a small staff and frequent television appearances. He has largely ignored Iowa to burrow into New Hampshire, a state where independent voters can cast ballots in the primary. Mr. Christie has made an aggressive push for those voters, who are more open to his anti-Trump message. This fall, organizations aligned with his campaign ran ads urging Democrats in the state to become “undeclared” voters and back his bid.

But as the deadline to switch party registration has passed, Mr. Christie has shown signs of weakness. In recent weeks, he has barely cracked 10 percent in polling in New Hampshire. It remains unclear whether he will be on the ballot in every state. Last week, officials said he had failed to collect enough signatures to qualify to be on the ballot in Maine. Mr. Christie plans to appeal the ruling.

Campaigning in New Hampshire, Mr. Christie said his path to the nomination would involve winning the state and then focusing on Michigan, which holds its primary in late February. He pointed to Mr. McCain’s 2008 campaign in New Hampshire as the model for victory. “All he did was come to New Hampshire, get in a Suburban and went from town to town to town, into town hall meetings, and he went on to win,” he said.

As Mr. Christie cracked jokes and took questions from voters, he remained adamant that he was in the race to win the nomination. The other candidates, he said, were “battling like animals to be in second place” — a line that drew chuckles from the crowd gathered in a packed reception room at a small restaurant in Concord.

“You know what we call second place in New Jersey? The first loser,” Mr. Christie said, as voters shouted out the answer in unison with him. “If you want to win, you got to beat the guy who’s in front of you.”

His appeal won support from some independent New Hampshire voters and even Trump Republicans. “He’s the only one that shows, in my mind, the strength and fortitude needed to run this country,” said Ralph Mecheau, 69, an independent voter who met Mr. Christie at a gathering of a state employees’ union. “If you can’t stand up to Trump, then how are you going to stand up to others?”

Gary Morrison, a 27-year-old Trump voter, who is a member of the state employee union, said he came out of the union town hall as a Christie supporter, and liked Mr. Christie’s policies on gun violence that focused on enforcement of laws already on the books and increased support for mental health care instead of adding more gun control laws.

“The way I look at it is just making sure that they can’t just take away stuff,” Mr. Morrison said.

Mr. Christie said that if he failed to notch a big victory in New Hampshire he would rethink his pledge to keep his campaign going until the Republican convention in July.

That’s far too long for some strategists, who said they wanted Mr. Christie to consider a much shorter timetable.

“He probably has the toughest path to the nomination, and you just have to face that reality sooner than later,” said Kevin Madden, a Republican strategist who worked on Mitt Romney’s 2012 presidential campaign. “Ideally, it would have been facing that reality yesterday, or a month or two months ago.”

Jazmine Ulloa contributed reporting.