Trump disregarded the criticism in a Twitter post, where the president noted that he had "won big" and Romney had not, urging the senator-elect to "focus on Border Security" and "be a team player". He lists some of the ways Trump has failed in his eyes and declares that Trump's "conduct over the past two years, particularly his actions this month, is evidence that the president has not risen to the mantle of the office".
"With the nation so divided, resentful and angry, presidential leadership in qualities of character is indispensable, " he said in the column, which was published on Tuesday evening. Then, after Trump was elected president, Romney dined with Trump and his then-chief of staff Reince Preibus at the Jean-Georges restaurant in Trump Tower.
The White House did not respond to a request for comment, but Trump fired back in a tweet early on Wednesday morning that took aim at Romney's loss in the 2012 presidential elections.
Successfully blocking Trump's re-nomination, said Williams, would feed Romney's "fantasy of being president, even if that means destroying our party and denying President Trump re-election".
The world "needs American leadership", he argued, and "the alternative. offered by China and Russian Federation is autocratic, corrupt and brutal".
He reminded those attending that he endorsed Romney in his Senate run.
Romney changed his mind about Trump later on, calling the then-president elect a "man who can lead the USA to a better future", back in November 2016.
"So you're not on board because the senior senator from Utah, Mike Lee, said he's likely going to endorse the president", Tapper added.
Romney, who is scheduled to be sworn into the Senate on Thursday, delivered a scathing condemnation of Trump in a Washington Post opinion piece, charging that he lacks the character to lead.
'Dishonesty is Donald Trump's hallmark, ' Romney added at the time, venting about Trump's 'bullying, the greed, the showing off, the misogyny, [and] the absurd third-grade theatrics'. His op-ed was a shallow political miscalculation and a pathetic attempt to be the center of attention.
After the election, Romney congratulated Trump.
Former White House press secretary Ari Fleischer wrote in a tweet of his own: "I'm disappointed in Mitt Romney". McDaniel wrote in a tweet Wednesday that her uncle's "attack" played into the hands of Democrats and the media. The president said Romney "should be happy for all Republicans" and should be "a TEAM player".
Other Republicans haven't been willing to go along, as Trump continues to have a passionate and vocal base of support among a significant segment of GOP voters.