Trump urging longest-serving Republican senator to run for re-election

— -- President Trump is going all-in to encourage the longest-serving Republican senator, 83-year-old Orrin Hatch of Utah, to run for an eighth term.

It's a move which also is being seen in some political circles as a shot at long-time nemesis Mitt Romney who's been angling to become Hatch's replacement.

"You are a true fighter, Orrin, I have to say," Trump said Monday during his announcement in Salt Lake City rolling back the scale of two national monuments in Utah.

"We hope you continue to serve your state and your country in the Senate for a very long time," Trump said.

Hatch, coming off a big win after the tax reform bill drafted by his committee cleared the Senate on Friday, shared a round-trip flight with the president on Air Force One on Monday. And on Thursday, Hatch in a press release said the president accepted his invitation to come to Utah and that the president told him on a phone call last month "I'm approving the Bears Ears recommendation for you, Orrin."

Amidst a sea of Congressional Republicans increasingly frustrated with the president, Hatch has consistently remained a Trump loyalist ever since the 2016 presidential campaign.

Just last week, after Trump sparked swift backlash when he retweeted three videos containing anti-Islamic content from a leader of a far-right British political group, Hatch quickly came to the president's defense.

"He's been one of the best presidents I've served under," Hatch, who took office during the Carter administration, said.

But the president's reciprocal strong public support for Hatch is not just a vote of confidence in the Utah senator. It also has the effect of sending a not-so-veiled message to Romney, whose name has been floated as a potential replacement for Hatch should he retire.

Romney, the 2012 Republican presidential candidate, has long been critical of Trump. Last year, he referred to Trump as a phony and a fraud during remarks at the University of Utah, and implored people not to vote for him.

During a tour of the Latter-day Saints Church food services facility in Utah, Trump was asked if he was sending a message to Romney by encouraging Hatch to run for re-election.

The president, referring to Romney, replied: "He's a good man."

ABC News has reached out to a Romney spokesperson for comment but has not received a response.

A spokesman for Hatch says the senator plans to announce a final decision by the end of the year.

“Over the past year the President has encouraged Senator Hatch to consider running for re-election a number of times, because of his leadership position and ability to advance their shared Republican agenda," Hatch spokesman Matt Whitlock said in a statement to ABC News.

"Senator Hatch is one of the most effective legislators of all time and has worked very effectively with President Trump’s administration," he continued.

But Hatch is also a fan of Romney's. Earlier this year in an interview with National Journal, Hatch addressed whether he'd support Romney if he ever ran to replace him in the Senate.

“If I could get a really outstanding person to run for my position, I might very well consider [retiring],” Hatch said, adding, “Mitt Romney would be perfect.”

A source with knowledge of the matter told ABC News that "while it may be entirely true that Trump dislikes Mitt, if there's anyone who can bridge the divide, it's Orrin."

"Keep in mind that [Hatch] was the only person in Utah to stick with Trump through the campaign. He never uttered a negatively critical word about Trump," the source said.