Jeffrey Becker/USA Today
Florida Gov. Ron DeSantis and Iowa Gov. Kim Reynolds attend the game between the Iowa State Cyclones and the Iowa Hawkeyes at Jack Trice Stadium in Ames, Iowa, on September 9, 2023.
CNN  — 

Iowa Gov. Kim Reynolds will endorse Florida Gov. Ron DeSantis in the 2024 Republican primary at a pre-debate rally in Des Moines, Iowa, on Monday night, sources familiar with the matter told CNN.

The DeSantis campaign is promoting Reynolds’ presence at the event on X, formerly known as Twitter.

Reynolds initially indicated she would likely remain neutral in the GOP primary race, but more recently has signaled willingness to back a candidate.

Reynolds will also join DeSantis on Tuesday for a meet-and-greet in Davenport, Iowa.

The Des Moines Register and NBC News were first to report the endorsement.

Reynolds’ popularity among Republican voters in Iowa could grant DeSantis a necessary boost if he hopes to compete against the far-and-away frontrunner in former President Donald Trump, with the Iowa caucuses – the kickoff to the Republican primary – now less than 100 days away.

Trump’s campaign said in a statement after Reynolds’ endorsement that the governor had “promised her constituents that she would remain neutral in the race, yet she has completely gone back on that promise. Regardless, her endorsement will not make any difference in this race.”

Polls from Iowa in October showed Trump ahead of DeSantis – the next-closest contender – by 30 points, with Trump supported by nearly half of likely Republican caucus-goers.

The DeSantis campaign’s hope is that a near-victory or outright win in Iowa will clear the field and reset the GOP primary as a two-person fight with Trump, which is why DeSantis is prioritizing Iowa over other early battlegrounds.

DeSantis’ campaign recently moved one-third of its Tallahassee campaign staff to Des Moines and the Florida governor has pledged to visit all 99 counties in the state. As of late last month, he had visited 83, he told CNN’s Kaitlan Collins.

“You shake the hands, you ask the questions, that is not something that you will necessarily see in polling. It is something that comes out when people make their decisions to caucus, so we’re doing it the right way. I’m going to be the only candidate that does all 99 counties,” DeSantis said on “The Source.”

A super PAC supporting DeSantis, Never Back Down, has spent $9.8 million boosting the governor on Iowa’s airwaves, as of early last month, more money than any other political committee or campaign.

Several notable conservative Iowans quickly offered their thoughts on the endorsement Sunday, with influential Iowa evangelical leader Bob Vander Plaats calling it a “game changer” for the primary.

“She is exceptionally popular and a great competitor,” Vander Plaats said of Reynolds’ influence in Iowa. “She wouldn’t endorse unless she saw a path to victory.”

And conservative Iowa radio host Jeff Angelo, whose popular show regularly brings on Republican presidential candidates, said that while he expects Trump will still win in Iowa, Reynolds’ backing “definitely helps” DeSantis’ efforts.

While Trump has boasted sustained support in Iowa, the state’s governor has for months felt differently about the leading candidate. In July, Trump lashed out at Reynolds for remaining neutral and for appearing alongside other candidates who had invited her to events across Iowa.

The former president in a social media post claimed credit for her ascent to the governorship and chastised her for not supporting him. Reynolds, as the state’s lieutenant governor, succeeded Gov. Terry Branstad in 2017 after he became Trump’s ambassador to China, and she was elected to a first full term the following year.

The other Republican presidential candidates immediately looked to ingratiate themselves to the popular governor against Trump’s attacks. DeSantis on a stop in Iowa in July said he would consider Reynolds as a potential running mate if he wins the nomination. He called her “one of the top public servants in America.”

On a call with Iowa media outlets in late October, DeSantis said a Reynolds endorsement “would be a huge get.”

“Obviously, I would love to have her support, formal support. I think that it would be very, very meaningful.”

This story has been updated with additional information.

CNN’s Jack Forrest, Steve ContornoAlayna TreeneJeff ZelenyDaniel Strauss and Kristen Holmes and Aaron Pellish contributed to this report.