Top Republican Sen. John Barrasso endorses Donald Trump

Sen. John Barrasso has became the highest-ranking Senate Republican to endorse former president Donald Trump’s reelection bid just days out from the Iowa caucuses.

"America was better off under President Donald Trump's leadership,” Barrasso said in a statement Tuesday night. "Working with Republicans in Congress, President Trump created the strongest economy of a generation, secured our Southern Border against a lawless drug and crime invasion, and made America an energy dominant superpower."

The Wyoming lawmaker also attacked Biden over inflation.

Trump thanked him on his social media platform.

"To know John is to both like and respect him, a truly extraordinary man," Trump said on Truth Social.

Barrasso drew criticism from former New Jersey GOP Gov. Christie Wednesday night. As he announced he was suspending his campaign that had been aimed at stopping Trump, Christie slammed the recent endorsements from Barrasso and House Republican Whip Tom Emmer.

“They know better. I know they know better,” Christie said.

Barrasso is the No. 3 Senate Republican, behind Minority Leader Mitch McConnell of Kentucky and Minority Whip John Thune of South Dakota. Barrasso, along with Thune and Texas Sen. John Cornyn, is viewed by some as one of McConnell's possible successors should Senate Republicans lose confidence in their leader after the November election.

Thune previously backed South Carolina Sen. Tim Scott’s now-shuttered campaign, while McConnell has demurred from making a presidential endorsement so far.

But Barrasso, who is up for reelection himself this year in deep-red Wyoming, is not alone in the Senate. Twenty of the 49 Republican senators have publicly declared their support for Trump.

Trump remains the frontrunner ahead of the first state presidential ballots, continuing to consolidate support from key party figures such as Barrasso.

Not one senator has yet thrown support behind one of Trump’s nearest GOP rivals. Former South Carolina Gov. Nikki Haley and Florida Gov. Ron DeSantis both trail Trump by double digits in national polls and also have fewer endorsements in the House and from governors.

Speaker Mike Johnson is among almost 100 members of the House of Representatives who have endorsed Trump. House Majority Leader Steve Scalise and House Majority Whip Tom Emmer endorsed him earlier this month, giving Trump an endorsement sweep of House GOP leadership.

Scalise and Emmer, the No. 2 and No. 3 House Republicans, endorsed Trump months after he helped sink their separate bids for House Speaker.

The former president spread doubts about Scalise’s health, invoking the congressman’s cancer diagnosis. And he publicly disparaged Emmer amid his speakership campaign. Emmer withdrew his candidacy hours after he was nominated.

Despite Barrasso’s backing, securing the endorsements of the full Senate GOP leadership heading into primary season may be more of a challenge for Trump. Along with McConnell and Thune, leadership members Sens. Shelley Moore Capito and Joni Ernst are also still neutral.

ABC News' Allison Pecorin contributed to this report.