President Trump gave his full backing to 2012 Republican presidential nominee Mitt Romney on Monday, saying Romney’s bid for a Senate seat from Utah “has my full support and endorsement!”

The president’s tweet suggested he may have buried the hatchet, at least temporarily, with the GOP foe who called Trump a “phony” and a “fraud” in 2016. Trump wrote Monday evening that Romney “will make a great Senator and worthy successor” to the retiring Orrin Hatch.

In response, Romney tweeted, “Thank you Mr. President for the support. I hope that over the course of the campaign I also earn the support and endorsement of the people of Utah.”

Romney, who served as Massachusetts governor from 2003 to 2007, announced his Senate run on Friday. The 70-year-old is a heavy favorite to hold the seat for the Republicans.

Trump’s endorsement of Romney marked another twist in the complex relationship between the two men. Romney was a vocal critic of Trump during the 2016 presidential campaign, labeling the businessman “a phony [and] a fraud [whose] promises are as worthless as a degree from Trump University.”

In response, Trump tweeted reminders that Romney had sought his endorsement during Romney’s failed run for the presidency four years earlier. In June of that year, Trump tweeted that Romney had “choked like a dog” in losing to former President Barack Obama.

After Trump’s victory, Romney was rumored to be a contender to be secretary of state. In an unusually public interview process, Romney was seen dining with Trump in New York City and visiting the president-elect at his golf club in suburban New Jersey. Ultimately, Trump tapped Rex Tillerson for the post of America’s top diplomat.

Since then, Romney has repeatedly criticized the Trump administration, particularly after Trump’s response to the actions of white supremacists in Charlottesville, Va., last summer. Among the president’s comments: “Especially in light of the advent of Antifa, if you look at what’s going on there, you know, you have some pretty bad dudes on the other side also.”

Romney also broke with the White House over Trump’s endorsement of Alabama Senate candidate Roy Moore amid accusations of sexual misconduct against him. In the run-up to the December special election, Romney stated that Moore’s election “would be a stain on the GOP and on the nation.”

The Associated Press contributed to this report.