By STEVE PEOPLES (AP National Political Writer)

CONCORD, N.H. (AP) — Donald Trump’s effort to march to the Republican presidential nomination faces perhaps its greatest challenge on Tuesday when voters in New Hampshire hold the first-in-the-nation primary.

The former president enters the contest emboldened by his record-setting performance in last week’s Iowa caucuses. But New Hampshire has a more moderate political tradition and primary rules that allow unaffiliated voters to participate in the race. Trump-backed MAGA candidates have struggled here in recent years.

Nikki Haley is hoping to capitalize on those vulnerabilities. The former U.N. ambassador is the only candidate left in the GOP primary aiming to defeat Trump outright. After a disappointing finish in Iowa, Florida Gov. Ron DeSantis is effectively surrendering new Hampshire and focusing on South Carolina’s Feb. 24 primary.

A Haley victory would usher in a more competitive phase of a primary that Trump has so far dominated. A Trump win, however, could create a sense of inevitability around the prospect that he could become the GOP nominee for the third consecutive time.

Don’t forget that Democrats have a primary, too. President Joe Biden is not on the ballot, having made South Carolina the first formal stop on the Democratic primary calendar. But New Hampshire is sticking to tradition and hosting its own Democratic primary anyway.

Here’s what we’re watching for on Tuesday:

If Trump’s rivals can’t beat him in New Hampshire, they may not be able to stop him anywhere else.

Tuesday’s election has essentially become a one-on-one fight between Trump and Haley, which is exactly what Trump’s Republican critics have been clamoring for. Haley appears competitive and enjoys support among moderate voters and independents. She’s also earned the backing of popular New Hampshire Gov. Chris Sununu.

Still, Trump remains the favorite.

Sensing a knock-out blow, the former president has called in his growing army of prominent supporters in recent days to help demonstrate his strength. South Carolina Sen. Tim Scott, Trump’s former opponent, endorsed Trump at a New Hampshire rally over the weekend. New York Rep. Elise Stefanik and Ohio Sen. J.D. Vance stumped for Trump on Saturday before an appearance from South Carolina Gov. Henry McMaster.

A significant number of New Hampshire Republicans insist they will never support Trump. And without a competitive Democratic primary in the way, many left-leaning unaffiliated voters could decide to support Haley. But that doesn’t change the fact that Republican primary elections are typically decided by Republicans, and Trump’s grip on the base appears stronger than ever.

Still, New Hampshire loves a comeback story (just ask Bill Clinton), so we wouldn’t rule anything out.

More than any issue or shortcoming, Trump’s fate may be tied most to who actually shows up to vote on Tuesday.

Iowa saw one of its lowest turnouts in recent history in last week’s caucuses. Low turnout elections typically favor the candidate with the strongest support among the party’s base. And in 2024, that’s Trump.

But Haley’s team has been trying to expand the New Hampshire electorate by appealing to less-ideological moderate Republicans and left-leaning independents.

New Hampshire law allows unaffiliated voters to participate in either party’s nomination contest. Democrats are not allowed to vote in the GOP primary, although voters had an opportunity to change their registration back in October.

Haley needs a large turnout to have a chance on Tuesday. And that’s exactly what state officials are expecting.

New Hampshire Secretary of State David M. Scanlan predicted that 322,000 voters would participate in the Republican primary, which would be a record high. On the Democratic side, he’s expecting just 88,000 given that there’s virtually no competition.

To defeat Trump, Haley probably needs more than a record-high turnout overall — she needs to bring out unaffiliated voters in record numbers, too. Trump’s team is skeptical. And history is not on her side.

It will be hard to ignore DeSantis’ decline once all the votes are counted on Tuesday.

The Florida governor visited the state for the first time in June as a front-runner in the 2024 primary. Seven months later, he’s been forced to surrender New Hampshire before a single vote is cast because of his dismal numbers here following his 30-point drubbing in Iowa.

DeSantis actually spent the weekend campaigning in South Carolina, which hosts its primary election in five weeks, to try to distance himself from what’s expected to be an ugly finish here.

We’re curious whether DeSantis’ departure actually ends up helping Trump, given that most of DeSantis’ supporters had positive views of the former president.

It’s also worth wondering if Tuesday marks the final primary election day for DeSantis as a 2024 candidate. During a brief appearance in New Hampshire last week before he sped to South Carolina, he said he would only continue to stay in the race if there was a path to victory.

If he’s embarrassed again on Tuesday, his shrinking path may disappear altogether.

Publicly and privately, Democratic leaders have repeatedly acknowledged that they fear Haley much more than Trump in a prospective general election matchup against Biden. We’re about to find out whether Republican primary voters agree.

Haley has spent months telling voters that, without Trump’s chaos and political baggage, she would be better positioned to defeat Biden in November. That argument didn’t help her much in Iowa, where she finished just behind DeSantis.

She’s betting that voters in swing-state New Hampshire will place more value on her longer-term political appeal. Sununu, New Hampshire’s popular GOP governor, has been at Haley’s side for weeks reminding voters of Trump’s dismal record in national elections ever since he entered the White House.

It’s unclear if the message has resonated.

If it doesn’t, it’ll be because Trump has effectively convinced Republican voters that he — not Haley — is the most electable general election candidate. That’s a risky bet, given his extraordinary legal problems, the stunning attack he inspired on the U.S. Capitol and his demonstrated record of alienating suburban voters in successive elections.

Biden’s unpopularity is no doubt muddying the issue.

Still, New Hampshire voters have an opportunity to cast a strategic vote Tuesday based on the one issue that seems to matter more than all else in today’s politics: the ability to beat the other side.

It may not be the headline, but New Hampshire Democrats are voting for their presidential nominee on Tuesday as well. And as much as Biden’s team wants you to think they don’t care about the outcome, they’re paying attention.

Biden won’t be on New Hampshire ballot, of course.

He’s avoiding New Hampshire altogether after pushing the Democratic National Committee to break tradition and award the nation’s opening primary to South Carolina, a much more diverse state that’s set to vote on Feb. 3. Furious about Biden’s decision, the “Live Free or Die” state ignored the president’s wishes and will host its own unsanctioned Democratic primary anyway.

There are several lesser known Democrats on the ballot, including Rep. Dean Phillips, D-Minn., and progressive activist Maryanne Williamson. Eager to demonstrate Biden’s strength despite his absence, the president’s allies in the state have been encouraging voters to write in Biden’s name.

The outcome will have no bearing on the number of delegates needed to secure the Democratic nomination. But an underwhelming finish, even in a write-in campaign, would represent an unwanted embarrassment as Biden tries to improve his political standing heading into the fall campaign.