Utah Republican Sen. Orrin Hatch announced on Tuesday that he will not seek re-election later this year, clearing the way for Mitt Romney—a top critic of President Donald Trump—to run for, and likely win, the seat.

“Every good fighter knows when to hang up the gloves. And for me, that time is soon approaching,” Hatch, the president pro tempore of the Senate, said in a video posted to Twitter. “That’s why after much prayer and discussion with family and friends, I’ve decided to retire at the end of this term.”

Hatch, 83, is the longest serving GOP senator and serves as the chairman of the Senate Finance Committee, a post that allowed him to spearhead successful efforts to overhaul the U.S. tax code. He first entered the Senate in 1977. Recently, Hatch won praise from Trump over his efforts to push the tax reform legislation over the finish line. Hatch returned the favor, calling Trump “one heckuva leader” and one of the best presidents “maybe ever.”

The love fest led to speculation that the senator would seek re-election. That speculation grew when Trump tried to encourage Hatch to do so, ostensibly as a way to block Romney, the 2012 GOP presidential nominee, from running for the seat.

But the persuasion campaign was not sufficient.

A source close to Romney told The Daily Beast that he is indeed likely to run for Hatch’s seat though an announcement was not likely to be soon, out of deference to retiring senator.

“They were waiting on a decision,” the source said. “They didn’t know what it was going to be. I think they’re surprised it came this quickly. But the expectation is he will run now.”

Romney himself furthered that speculation on Tuesday afternoon when, just hours after Hatch’s announcement, he changed his location on Twitter from Massachusetts to “Holladay, UT.”

A Romney bid would present a tricky dilemma for the White House. In the 2016 campaign Romney gave a high profile speech calling Trump a “con man.” In recent months, the former presidential candidate has been a vocal critic of Trump, taking to Twitter to blast the president on a variety of subjects.

Trump has not hid his disdain for Romney. In fact, he has at times seemed to revel in tormenting him, dangling the post of secretary of state in front of him before giving it to Rex Tillerson. (Trump’s longtime confidant, Roger Stone, claimed Trump interviewed Romney merely to “torture” him; while Trump’s aide, Kellyanne Conway, publicly questioned the merits of bringing Romney to Foggy Bottom even as he was under consideration for the post.)

White House Press Secretary Sarah Sanders said on Tuesday that Trump was “very sad” to see Hatch decide to retire. And the source close to Romney said that they fully expect the president and, by extension, his former top strategist Steve Bannon, to continue to try meddle in the Republican primary in Utah.

But there is confidence in Romney’s orbit that such efforts won’t be effective, at least not to the extent that they were in other primaries—most notably, Alabama.

“Utah is not Alabama and Mitt Romney is very very popular with not just Utah Republicans but Democrats,” the source said.

Among the names being discussed to run a potential Romney campaign include Matt Waldrip, who worked on Romney’s finance team during his second presidential run in 2012 and who currently is with Solamere Capital, an investment firm run in part by Romney’s son Tagg. Waldrip did not return a request for comment.

Romney’s team also could benefit from the political consultancy group Poolhouse Strategies, which was started by his former aide Will Ritter and which successfully helped Utah Republican Rep. John Curtis win the special election to replace former Rep. Jason Chaffetz. Ritter did not return a request for comment.

Utahns will vote on June 26 in a primary election to choose the Democratic and Republican nominees—a new voting system in the state that has proven to help more moderate candidates like Curtis win . In 2010, under the previous voting system, Mike Lee defeated then-Sen. Bob Bennett (R-UT) in a nominating contest that relied on delegates at a statewide convention choosing the Republican nominee. Lee, one of the most conservative members of Congress, went on to become a U.S. senator.