Utah Sen. Mitt Romney (R) refused to reveal to reporters Friday if he will endorse President Trump in the upcoming presidential election.

The former governor and failed presidential candidate told a group of reporters that he did not know if he would issue an endorsement in 2020.

“I don’t think endorsements are worth a thimble of spit,” he told the media during an appearance at the annual E2 Summit with political and business leaders in Park City. “I wouldn’t be surprised if I stay out of the endorsements.”

Romney did not close the door on potential endorsements completely but affirmed the belief that a sitting president overseeing a time of economic prosperity maintains an upper hand. However, Romney said victory is “not a sure thing.”

“I think the attitude here has got to be the same as across the country, which is the president will surely be the Republican nominee, and an incumbent in a growing economy is more likely to win than to lose. But it’s not a sure thing,” he explained.

This is far from the first time Romney has refused to endorse Trump. The two went head-to-head during the contentious 2016 election. Trump called Romney “one of the dumbest and worst candidates in the history of Republican politics” after Romney demanded he release his tax returns earlier in the year:

Mitt Romney, who was one of the dumbest and worst candidates in the history of Republican politics, is now pushing me on tax returns. Dope! — Donald J. Trump (@realDonaldTrump) February 25, 2016

In turn, Romney called Trump a “phony” and “fraud.”

“He’s playing the American public for suckers: He gets a free ride to the White House and all we get is a lousy hat,” Romney tweeted in March 2016:

Here's what I know. Donald Trump is a phony, a fraud. His promises are as worthless as a degree from Trump University. (1/2) — Mitt Romney (@MittRomney) March 3, 2016

He's playing the American public for suckers: He gets a free ride to the White House and all we get is a lousy hat. (2/2) — Mitt Romney (@MittRomney) March 3, 2016

When it came time to put personal animosity aside, Romney refused, instead writing his wife, Ann, on the 2016 ballot.

However, when he ran for senator, Romney eagerly accepted Trump’s support:

.@MittRomney has announced he is running for the Senate from the wonderful State of Utah. He will make a great Senator and worthy successor to @OrrinHatch, and has my full support and endorsement! — Donald J. Trump (@realDonaldTrump) February 20, 2018