As the last major challenger in Donald Trump's way, Nikki Haley is hoping New Hampshire voters feel so strongly about keeping the former president away from the White House that they turn out to support her in large numbers.

“America does not do coronations,” Haley said at a VFW hall in Franklin, joined by her daughter and son-in-law. “Let's show all of the media class and the political class that we've got a different plan in mind, and let's show the country what we can do."

It's an uphill battle for the former UN ambassador and South Carolina governor. Most conservatives want to give Trump another chance at beating President Joe Biden despite Trump's 2020 election loss and the 91 felony charges he faces in four separate indictments.

With voting about to begin in New Hampshire, almost every top Republican has lined up behind Trump, and polls in New Hampshire suggest he leads Haley in a state uniquely suited to her strengths.

Trump planned to hold his last rally before the election Monday night. He started the day in New York for his defamation trial after an earlier jury determined he had sexually abused a columnist in the 1990s, but the session was cancelled due to a juror's illness.

Trump was being joined on stage Monday night by three of his former opponents who have now endorsed him: South Carolina Sen. Tim Scott, tech entrepreneur Vivek Ramaswamy and North Dakota Gov. Doug Burgum. The show of force is part of a broader effort by Trump's team to lock up the primary and demonstrate the party is rallying around him.

On paper, Trump had seemed more vulnerable in New Hampshire than in any other early voting state on the primary calendar. Though voters here supported him by a wide margin in 2016, the state has long been known for its moderate tradition, including allowing unaffiliated voters to participate in GOP primaries. And Haley had been on the rise, prompting Trump's campaign and its allies to spend millions trying to blunt her momentum.

Thalia Flores, a former Democrat who manages retail stores, changed her voter registration to undeclared last fall and plans to vote in New Hampshire's Republican presidential primary against Trump. She says she would support Haley over President Joe Biden if given the chance, even though she has never before voted for a Republican presidential candidate.

But on the eve of the contest, she worries the primary is "a long shot” with not enough support for Haley among traditional conservatives to beat Trump.

“What do the Republicans want?” Flores asked at a packed Haley rally over the weekend. “Are they diehard Trump or do they want the White House?”

Florida Gov. Ron DeSantis' exit turned the state into the one-on-one contest between Trump and Haley that she and a long line of anti-Trump Republicans had said they wanted.

But some evidence suggests Trump could be better positioned to capitalize on DeSantis' exit than Haley. According to AP VoteCast, DeSantis supporters in Iowa overwhelmingly described themselves as conservative and Trump outperformed Haley 53 per cent to 13 per cent among that group.

DeSantis immediately endorsed Trump upon dropping out, saying it was clear to him Republican voters preferred the former president.

By Monday, Montana Sen. Steve Daines, who heads the GOP's Senate campaign committee, called him “the presumptive nominee.”

Never before has a presidential candidate won primary contests in both Iowa and New Hampshire and failed to secure the party's presidential nomination.

“Basically after New Hampshire, it's an academic exercise," said Chris LaCivita, Trump's senior adviser. "This is really where it matters."

Trump's confidence comes even as respected Republicans like New Hampshire Gov. Chris Sununu warn of dire political consequences.

“Republicans are tired of losing. We're tired of losers. We're tired of Donald Trump," Sununu told roughly 500 Haley supporters gathered in the state's largest city over the weekend.

On Monday, Haley spoke on New Hampshire Today with host Chris Ryan and compared Trump to Biden, bringing up how Trump has confused her with former U.S. House Speaker Nancy Pelosi, mistakenly said he ran against former President Barack Obama, and warned about Biden leading the country into World War II, which was fought between 1939 and 1945.

“When you have two 80-year-olds running for president, you are going to see decline,” she said. “It's natural. It's what happens.”

At the same time, Haley's campaign has been lowering expectations for New Hampshire after insisting for weeks that an outright victory against Trump was possible.

“Beating Donald Trump is not easy. He is a juggernaut,” Haley campaign manager Betsy Ankney said at a weekend event hosted by Bloomberg. “But how do you eat an elephant? One bite at a time. We have to continue to show incremental growth and progress. We are the last man - woman - standing against him.”

Still, the tens of thousands of voters who have packed into Trump's New Hampshire rallies in recent days don't seem to be worried and he makes little effort to lower expectations.

Eric Holmstrom, a 43-year-old Republican from Goffstown who supports Trump, said he sees the former president's back-and-forth travel from the courtroom to campaign events as a sign of why he's the best person to be the party's nominee.

“I mean, this guy's stamina is unmatched. And that's — we need strength,” Holmstrom said. “We need unity. We need strength. And we need stamina. And right now, the unity isn't there but it's happening.”