President Donald Trump gave his blessing to Mitt Romney’s Senate run Monday night.

Shortly after the president’s endorsement, Romney tweeted his gratitude for the nod.

Romney announced Friday that he will seek the seat expected to be vacated by Sen. Orrin Hatch, R-Utah.

The president’s Romney endorsement was not a sure bet, given the often contentious history between the two. Romney responded to Trump’s presidential campaign by calling him a “phony” during a 20-minute speech condemning the then-candidate at the University of Utah in 2016.

Trump responded at a campaign rally, saying Romney was “begging” for his endorsement during the former Massachusetts governor’s 2012 presidential run.

The feud didn’t stop when Trump was elected. Romney has routinely weighed in on the president’s unorthodox comments, including his brash statements on immigration.

Trump, in turn, has gone after Romney, saying he "choked like a dog" in his 2012 run for president. But the two have also been cordial. They played golf together shortly after Trump won the 2016 election.

President-elect Donald Trump, center, eats dinner with Mitt Romney, right, and Trump Chief of Staff Reince Priebus at Jean-Georges restaurant, Tuesday, Nov. 29, 2016, in New York. (AP Photo/Evan Vucci)

As the two hit the links, there was speculation that Trump would consider Romney for secretary of state before giving the Cabinet position to Rex Tillerson, who was then the Exxon Mobil Corp. president.

Romney and the president continued to be at odds as recently as December, when they clashed over Trump’s endorsement of Roy Moore, who ran unsuccessfully for U.S. Senate in Alabama amid allegations of inappropriate behavior with underage girls.

But in January, it was rumored that Trump urged Romney to replace Hatch, who had become a close ally to the president.