Ambassador Nikki Haley needs a win — or at least a close second-place finish — in New Hampshire next week to keep her campaign alive, but a Suffolk University/Boston Globe poll released Wednesday is casting further doubt that she can beat President Trump in the Granite State.

The poll shows Mr. Trump leading in New Hampshire with 50 percent support to Ms. Haley’s 34 percent. Florida’s governor, Ron DeSantis, trails in third place with 5 percent support. This is the first Granite State poll released since entrepreneur Vivek Ramaswamy and the Arkansas governor, Asa Hutchinson, dropped out of the race after poor showings in the Iowa caucuses.

The poll, though, contrasts sharply with other recent primary polls that show a much closer race in the Granite State. A second poll released this week by American Research Group, conducted before the Iowa caucuses, shows Ms. Haley tying Mr. Trump at 40 percent support. A University of New Hampshire poll released earlier this month showed Ms. Haley trailing Mr. Trump by seven points.

“The polling is giving people whiplash,” a political science professor at New England College, Nathan Shrader, tells the Sun. He says swings in polling have fueled the narrative that Ms. Haley will be a “comeback kid” because New Hampshire voters are “contrarian.”

Ms. Haley has set expectations high for her performance in New Hampshire, where Republicans are more socially moderate than in Iowa and where independent voters — the largest share of registered voters in the state — can vote in either party’s primary.

Undeclared voters are expected to cast ballots in the Republican primary in large numbers this year because the Democratic National Committee has declared the state’s Democratic primary “meaningless” and will not be awarding delegates based on the results. Ms. Haley told an audience earlier this month that New Hampshire voters would “correct” the mistakes of Iowa.

Mr. Trump won Iowa by a historic margin Monday night, earning more than 50 percent of the vote and winning all but one of Iowa’s 99 counties. Ms. Haley had come into caucus night with momentum and an expectation, based on a Des Moines Register poll, that she would finish in second place. Instead, she finished a close third behind Mr. DeSantis.

Ms. Haley nonetheless declared in a speech Monday night that the Republican presidential nominating contest “is now a two-person race.” If she doesn’t overperform in New Hampshire, that argument will be moot.

Mr. Shrader says he has more “confidence” in the Suffolk University poll than the others because it is rated higher by FiveThirtyEight and because the poll questioned an almost equal number of Republicans and undeclared voters. The American Research Group poll, by contrast, polled more than twice as many Republicans as independents.

“If Nikki Haley does have all this momentum among undeclared New Hampshire voters who can participate in the primary, she should have actually done better in the Suffolk poll,” Mr. Shrader says. “Nikki Haley claims a two-person race and she’s one of the two people. I see this as a one-person race.”

A Republican strategist in New Hampshire, Matthew Bartlett, tells the Sun this focus on Ms. Haley’s support among independents and Democrats is hurting her with Republicans. “It’s not helpful to have Bill Kristol’s voice weighing in or to have positive news coverage from the mainstream media,” Mr. Bartlett says.

“She needs to continue to go out there and remind people how she was the Tea Party darling in 2010, who Sarah Palin endorsed, who ruled South Carolina as a staunch conservative, so much so that Donald Trump himself sent her to the UN to lead MAGA foreign policy,” Mr. Bartlett says.  

Suffolk University will be releasing a new poll of 500 likely Republican primary voters each day until the New Hampshire primary on Tuesday.