Nikki Haley and Ron DeSantis square off Wednesday in high-stakes Republican presidential debate

Nikki Haley and Ron DeSantis are set to square off Wednesday in a slimmed-down Republican presidential debate that could go a long way toward determining if either one of them can mount a serious challenge to former President Donald Trump.

The former U.N. ambassador will be aiming to land more powerful blows on DeSantis after catching up to him in a string of polls in recent weeks as the first-in-the-nation Iowa caucuses loom less than six weeks away.

DeSantis, on the other hand, faces intense pressure to show he’s still got what it takes to battle Trump after a series of campaign setbacks and sagging poll numbers.

The fourth debate is the first contest since Haley picked up the crucial endorsement of the Koch network of big-money conservative donors, pumping millions into her campaign war chest.

Both contenders claim they can knock off Trump in a one-on-one battle and both say they would be a better bet to unseat President Biden in the November general election.

Pundits say Trump benefits from both candidates staying in the race as long as possible and dividing the votes of those who oppose giving him a third straight GOP nomination.

Trump has skipped all the GOP debates and has no plans to show up at the showdown set for 8 p.m. in Tuscaloosa, Alabama.

The former president says he is so far ahead in the polls that the nomination race is effectively over.

The fourth debate will include just four candidates in all, with entrepreneur Vivek Ramaswamy and ex-Gov. Chris Christie rounding out the field.

After Wednesday’s contest, one more debate is expected in early January before Iowa, where DeSantis says he needs a strong showing. There will be another contest before New Hampshire votes in the GOP primary.

Trump faces a March 3 trial date in his federal election interference case, meaning he will be likely on trial for seeking to overturn his loss in the 2020 elections as a big chunk of GOP delegates are selected in the Super Tuesday contests and a string of key primaries in following weeks.