Can Donald Trump's rivals defeat him in the Republican primary? Here's what they need to do for a 2024 upset

WASHINGTON — It's not impossible for former President Donald Trump's Republican rivals to catch up to him in the 2024 GOP primary – but at this point it will take a historic comeback.

The main challengers – former South Carolina Gov. Nikki Haley, Florida Gov. Ron DeSantis, former New Jersey Gov. Chris Christie and entrepreneur Vivek Ramaswamy − are taking different approaches as they chase Trump. The former president has long been the frontrunner in the Republican field, leading his fellow candidates by 50 percentage points in some national polls.

But the other White House hopefuls all have common challenges as they try to make up ground ahead of the Iowa caucuses on Jan. 15 and the New Hampshire primary on Jan. 23.

"This race is a marathon, not a sprint," Haley said Tuesday on X, the platform formerly known as Twitter.

Here's what you need to know about the obstacles Haley and other Republican candidates face as they compete with Trump.

Unite around one challenger

One way Trump's GOP rivals could target the former president is consolidating behind a single alternative.

That's easier said than done, though.

Haley and her campaign say DeSantis blew his chance to be the top alternative to Trump as he failed to gain traction among voters and fell behind Haley in several polls, especially in New Hampshire. Now, they say DeSantis is responding by attacking her.

“Ron DeSantis has not put one truthful ad up there about me," Haley told voters over the weekend in Iowa.

DeSantis accuses Haley of being too much of an "establishment" candidate to effectively challenge Trump, claiming she hasn't built up grassroots support among Republican voters across the country.

“She also cannot beat Donald Trump in 1-on-1 because she doesn’t have support from conservatives," the Florida governor told Fox News this week.

Christie says Haley, DeSantis and Ramaswamy have been too soft on Trump, especially over his four sets of criminal charges – to the point of saying they would support Trump if he wins the nomination and is convicted by a jury.

"That is the most important issue in this race," Christie told CNN, "because we can't beat Joe Biden with a convicted felon."

Finish second, at least, in Iowa and New Hampshire

Republican candidates – other than Trump – have often denigrated national polls. They say the real test comes when people actually vote and candidates have to perform.

That makes early voting states such as Iowa and New Hampshire critical.

DeSantis says he's confident his get-out-the-vote program in Iowa will lead to success that will carry over to New Hampshire. But an October Des Moines Register/NBC News/Mediacom Iowa Poll showed DeSantis and Haley tied with 16% support among likely Republican caususgoers in the state.

Haley appears to be on the rise in New Hampshire, trailing Trump by a margin of 44%-29% in a recent CBS News/YouGov poll. A good performance would propel her toward the Feb. 24 primary in her home state of South Carolina.

Christie is also banking on New Hampshire and believes a victory there would make him the Trump alternative.

But recent polls showed the former New Jersey governor lagging at least six points behind Haley and 28 points behind Trump in New Hampshire, despite having focused most of his campaign on the Granite State.

In any event, an outright victory by any challenger in Iowa and New Hampshire would totally transform the race.

Goad Trump into a debate

Opponents figure their best chance is to best Trump in a televised debate, but so far the former president has not given them the opportunity.

Trump skipped all four Republican primary debates in 2023. So now rivals are trying to pressure him into events that scheduled in Iowa and New Hampshire, accusing him of cowardice and taking voters for granted.

"Why don't you go ask him if he's going to get on a debate stage in Iowa," Haley said on ABC News' 'This Week.' "Why don't you go ask him if he's going to get on a debate stage in New Hampshire."

After accepting a debate invitation from CNN earlier this month, DeSantis told Iowa reporters that Trump is insulting the electorate: "If you’re not willing to debate in Iowa on the eve of the caucus, that shows the voters a lot about you and about your willingness to engage on these issues."

Is there anything Trump rivals can do?

Of course, DeSantis, Haley and other Republican rivals' options are limited.

Given Trump's hold on the party, current and former Republicans said there's little or nothing opponents can do to stop what some called his inevitable march to the nomination.

"There’s not a thing any of them can do," said Joe Walsh, a former Republican congressman from Illinois. "Not one damn thing."