Senate Minority Whip John Thune, the No. 2 Senate Republican leader, is endorsing former President Trump for reelection.

It’s a key win for Trump from the establishment wing of the Republican Party. The South Dakota Republican is Minority Leader Mitch McConnell’s top deputy in the Senate GOP.

‘The primary results in South Carolina make clear that Donald Trump will be the Republican nominee for president in this year’s pivotal presidential election. The choice before the American people is crystal clear: It’s Donald Trump or Joe Biden,’ Thune told Fox News Digital.

‘I support former President Trump’s campaign to win the presidency, and I intend to do everything I can to see that he has a Republican majority in the Senate working with him to restore American strength at home and abroad,’ he continued.

‘Together we must put an end to the disastrous Biden-Schumer agenda. Our country cannot endure another four years of Bidenomics, continued lawlessness at our southern border, and American weakness on the global stage.’

Thune and Trump spoke by phone on Saturday night after Trump’s commanding victory in the South Carolina Republican primary, a source familiar with the call told Fox News Digital.

It wasn’t clear before now whether Thune, who’s seen as one of McConnell’s potential successors to lead the Senate Republican Conference, would endorse either of the two major candidates for the 2024 GOP nomination. 

Like McConnell, he suggested he would support whoever Republican voters chose as their presidential nominee, but Thune has for the most part avoided mentioning the former president.

He previously endorsed South Carolina Sen. Tim Scott’s presidential campaign and was present at Scott’s launch event. Scott dropped out in November and endorsed Trump last month.

The Sunday announcement puts added pressure on McConnell, who has brushed off scrutiny on whether his frosty relationship with Trump would stop him from endorsing the ex-president in the Republican primary.

McConnell said at a press conference this month when asked about the race, ‘I’ve stayed essentially out of it, and when I change my mind about that, I’ll let you know.’

Both Thune and McConnell were targeted by Trump for criticizing his handling of the Jan. 6, 2021, Capitol riot and the 2020 election.

Thune won a landslide reelection victory for a fourth Senate term in 2022 despite Trump calling for a primary challenger against him.

His endorsement of the former president comes after Trump beat former United Nations Ambassador Nikki Haley in her home state primary on Saturday night. The ex-president won roughly 60% of the vote compared to 40% for Haley.