Romney was a frequent critic of Trump on the campaign trail. In March, he attacked the then-presidential hopeful as a "phony, a fraud," during a speech in Utah.
"His promises are as worthless as a degree from Trump University," Romney said. "He's playing members of the American public for suckers. He gets a free ride to the White House, and all we get is a lousy hat."
Fractures in the Trump transition team were noted by Conway in a tweet on Thanksgiving Day. She said she had received a "deluge" of comments on social media and in private communications from Trump loyalists worried that the president-elect might choose Romney as secretary of state.
"It's just breathtaking, in scope and intensity, the type of messages I've received from all over the country ... the number of people who feel betrayed to think that Gov. Romney would get the most prominent Cabinet post after he went so far out of his way to hurt Donald Trump," Conway said Sunday on http://www.cnn.com/2016/11/27/politics/conway-trump-romney-betrayed/ CNN's "State of the Union."
Conway is not the only top Trump adviser publicly balking over the decision to bring Romney into the Trump Administration.
Former Arkansas Gov. Mike Huckabee and former House Speaker Newt Gingrich last week criticized Romney in interviews with Fox News.
"He attacked (Trump) on a personal level about his character, integrity, his honor," Huckabee said, adding that choosing the former Massachusetts governor for secretary of state "would be a real insult to those Donald Trump voters who worked really hard."
Gingrich, meanwhile, questioned Romney's trustworthiness and highlighted his former presidential ambitions.
"You have to list out all the things he said and think, 'Is this guy really going to be loyal?'" Gingrich said. "Gov. Romney wanted to be president, not secretary of state, and you have to ask the question: When he goes overseas, is he going be the secretary of state for President Trump or is he going to be Mitt Romney's own secretary state?"