The former New Jersey governor Chris Christie’s decision on Wednesday to drop out of the presidential race shook up a contest for the Republican nomination that had appeared to be former President Donald J. Trump’s for the taking, giving a huge shot of adrenaline to Nikki Haley just five days before ballots begin to be cast in the monthslong nomination fight.
The most obviously altered battleground is likely to be New Hampshire, where Ms. Haley, the former governor of South Carolina and Mr. Trump’s first ambassador to the United Nations, is within striking distance of the former president. Even without his endorsement, many New Hampshire voters who planned to side with Mr. Christie as an opponent of Mr. Trump’s are likely to flip to Ms. Haley, as is potentially some of Mr. Christie’s leadership team.
But the jolt will have much broader implications, argued John Sununu, a former New Hampshire senator and the brother of the current governor, Chris Sununu, both of whom have endorsed Ms. Haley. A contest that has centered on Mr. Trump’s return and the fight between Ms. Haley and Gov. Ron DeSantis of Florida for second place will now focus squarely on the threat Ms. Haley poses to Mr. Trump’s coronation.
A memo that Mr. Trump’s campaign blasted out after Christie’s announcement on Wednesday night did just that, broadcasting what it called internal polling that showed Mr. Trump beating Ms. Haley in a head-to-head contest 56 percent to 40 percent.
“It changes the whole story to Donald Trump’s worst nightmare, which is having to campaign and run on substance against someone who’s balanced budgets, who’s been a strong conservative leader and who, at the same time, hasn’t left chaos wherever she’s gone,” Mr. Sununu said.
Voters in Iowa will caucus on Monday, with the New Hampshire primaries following on Jan. 23. Mr. Christie’s decision could push the few voters he has in Iowa toward Ms. Haley. But, perhaps more important, the final days before the caucus will focus more on the two-person dynamic between Ms. Haley and Mr. Trump, taking oxygen from Mr. DeSantis in the state where he needs it most.
Mr. Christie’s departure also makes a victory for Ms. Haley in New Hampshire a more plausible outcome, one that would buoy her not only going into Nevada, but also in her home state of South Carolina and beyond. A CNN Poll conducted by the University of New Hampshire and released this week indicated that 65 percent of Mr. Christie’s supporters would back Ms. Haley if their first choice were not in the contest.
Matthew Bartlett, a former Trump appointee and a Republican strategist who is unaligned in the race, said it was clear that Ms. Haley was obtaining “the final puzzle piece” as she puts together a broad coalition of Republicans that includes former Trump die-hards like Don Bolduc, a retired Army general who unsuccessfully ran for the Senate in 2022 on a hard-right platform, and “old Yankee Republicans” like Gov. Sununu and his brother.
“If she were to win New Hampshire, or even if she were to come in a very close second, that will be a seismic shock in the Republican Party,” Mr. Bartlett said.
To be sure, assuming that Ms. Haley would take an overwhelming number of Mr. Christie’s supporters could be overstating her power. Even Mr. Christie, in a “hot mic” moment that was accidentally broadcast over the livestream that preceded his announcement, said that Ms. Haley would still “get smoked.”
“She’s not ready for this,” he said.
His departure speech on Wednesday was almost as caustic toward Ms. Haley and Mr. DeSantis as it was toward Mr. Trump. He mocked Ms. Haley for failing to cite slavery as the cause of the Civil War and blasted all the candidates who had pledged to vote for Mr. Trump as the nominee, even if Mr. Trump is convicted of a crime. Ms. Haley was among them.
“Anyone unwilling to say he is unfit to be president of the United States is unfit themselves to be president of the United States,” Mr. Christie said — hardly a ringing endorsement for any of the remaining candidates.
Fergus Cullen, a former New Hampshire Republican Party chairman and now a city counselor in Dover, N.H., said that he had vacillated between the two candidates but that he had settled on Mr. Christie after Ms Haley had first promised to pardon Mr. Trump if he were convicted on any of the 91 felony counts he faces, then refused to rule out being his running mate.
Mr. Cullen had wanted Mr. Christie to stay in the race unless and until Ms. Haley at least renounced the vice presidency. Now, he said, “I will vote for Haley with zero enthusiasm.”
The sentiment has been echoed in interviews with independent voters at town hall-style events across New Hampshire. At a sports bar in Londonderry last week, Lois and Paul Keenliside said they were independents who felt a responsibility to elevate the best anti-Trump candidate. But after listening to Ms. Haley, they remained on the fence, concerned that she had not ruled out the possibility of running as Mr. Trump’s vice president. If she were to do so, Mr. Keenliside said, many independents “would feel betrayed.”
If nothing else, though, Mr. Christie’s supporters “don’t go to Trump,” said Greg Moore, the New Hampshire director for Americans for Prosperity Action, the well-funded super PAC backed by the billionaires Charles and David Koch, in an interview conducted on Sunday. The super PAC has endorsed Ms. Haley.
Internal polling from Americans for Prosperity Action, conducted last month, found Mr. Trump with a lead of 12 percentage points over Ms. Haley and the rest of the field. But in a two-person, head-to-head matchup, the poll showed them statistically tied.
The Trump campaign suggested that Mr. Christie’s withdrawal would pull Ms. Haley to the political left to woo his independent and Democratic-leaning voters, alienating most of the Republican electorate.
“Among New Hampshire Republican primary voters, Chris Christie is radioactive,” the campaign memo released on Wednesday said. “If his withdrawal was meant to help Nikki Haley, it will further polarize the primary to be a battle between the Trump conservatives and Haley’s D.C. establishment base.”
Randy McMullen, 69, who is one such independent, said that he was drawn to Mr. Christie and Ms. Haley because of what he saw as an ability to compromise and reach across the aisle. Mr. Trump was a nonstarter for him, he said, adding that the former president and his emulators were too intransigent.
“It’s MAGA or no way,” he said of Mr. Trump and his allies.
Beyond New Hampshire, the road becomes much steeper for Ms. Haley. Even in her home state of South Carolina, Mr. Trump remains “the prohibitive favorite” ahead of the Feb. 24 primary, said Matt Moore, a former South Carolina Republican Party chairman who had backed South Carolina’s senator, Tim Scott, before he left the race.
And, Mr. Moore noted, Mr. DeSantis could drop out before then, with the bulk of his voters likely moving to the former president. But winning tends to beget winning, and South Carolinians who had previously voted for Ms. Haley for governor but who now back Mr. Trump may be willing to take a second look as she storms out of New Hampshire.
As the first contests of the primary season approached, Mr. Christie began to hear more frequently from apprehensive Never-Trump voters who were drawn to his fearlessness in criticizing Mr. Trump but who worried that he was siphoning votes from a more viable candidate like Ms. Haley.
“What gives me a great deal of anxiety is that you and Governor Haley appeal to the same people,” Camron Barth, a 37-year-old 911 dispatcher, told Mr. Christie last week during a town hall event in Keene, N.H. “And so my question to you is: Do you think my anxiety about that is unfounded?”
“No,” Mr. Christie said. “I have the same anxiety.”
A victory for Ms. Haley in New Hampshire is no guarantee of her long-term viability. Then-Senator John McCain of Arizona upset the heavily favored George W. Bush in 2000, rocketing him into South Carolina, where more conservative voters and an organized Bush operation cut him down and virtually ended the race.
But before then, in 1992, Bill Clinton righted his scandal-plagued campaign in New Hampshire with a strong second-place finish, declaring himself “the comeback kid.”
“And the rest is history,” Mr. Bartlett said.
Jonathan Weisman, Nick Corasaniti and Jazmine Ulloa