"Ron is focused, he is principled, he is results driven," Reynolds told a crowd of cheering supporters at a rally in Des Moines where DeSantis also took the stage.

"And in short, what I love most about Ron is he gets things done."

The endorsement is unlikely to change the fundamental dynamics of the Iowa race, which Trump currently dominates. But the DeSantis campaign has been pursuing Reynolds' nod for months, according to several people close to the campaign, and endorsements from popular political leaders often move the needle by a few percentage points.

According to a Des Moines Register/Mediacom poll released in late October, 43% of likely caucusgoers planned to vote for Trump, while DeSantis and former U.S. Ambassador to the United Nations Nikki Haley were tied with 16% support. Other candidates were polling in the single digits.

The Midwestern state plays a pivotal role in the Republican nominating contest as it is the first to select a preferred nominee. Its caucuses, local party meetings where voters decide whom to support, take place Jan. 15.

Reynolds, 64, is popular among conservatives in Iowa. Some 81% of likely participants in the state's Republican caucuses approve of her, according to an August poll conducted by the Des Moines Register newspaper.

Much like DeSantis, Reynolds has leaned into "culture war" issues as governor. She has signed bills to restrict teaching of topics related to gender and sexuality in public schools and prohibited transgender students from using the bathrooms that align with their gender identity, among other measures.

While Reynolds supported Trump during his time in office and campaigned with him during his unsuccessful 2020 re-election bid, their relationship has deteriorated. In recent months, the former president publicly complained that Reynolds had not endorsed him and declined opportunities to appear with her.

In a Truth Social post on Sunday, Trump wrote that a Reynolds endorsement of DeSantis would mark "the end of her political career."

The endorsement comes two days before DeSantis takes the stage for the third Republican primary debate in Florida, which Trump is skipping.

Reuters and several other media outlets reported on Sunday that Reynolds would endorse DeSantis.

(Reporting by Gram Slattery; Editing by Cynthia Osterman)

By Gram Slattery