Former Trump campaign manager Kellyanne Conway on CNN. CNN President-elect Donald Trump's former campaign manager again strongly suggested on Sunday that his supporters would not back former Massachusetts Gov. Mitt Romney for secretary of state.

Kellyanne Conway, one of Trump's top advisers, told CNN's Dana Bash that while she hoped Romney would be a gracious secretary of state if selected, his aggressive criticism of Trump during the 2016 Republican primary did not sit well with the president-elect's supporters.

"It's just breathtaking in scope and intensity the type of messages I have received from all over the country," Conway said. "The number of people who feel betrayed to think that Governor Romney would get the most prominent Cabinet post, after he went so far out of his way to hurt Donald Trump — there was the Never Trump movement, and then there was Mitt Romney."

She added: "If president-elect Trump chooses Mitt Romney as his secretary of state, or whomever he chooses, that will have the full support and backing of all of us. I respect the brilliance and judgment and sheer instincts of president-elect Trump to form his Cabinet as he wishes. But I felt compelled to come forward on behalf of the people who were weighing in."

Conway argued that Romney "attacked [Trump's] character." She also noted that several of the former governor's staffers were highly critical of the now-president-elect and questioned whether Romney had the appropriate foreign-policy credentials to deserve the position.

"Has he been around the globe doing something on behalf of the United States, of which we're unaware?" Conway said. "I'm all for party unity, but I'm not sure that we have to pay for that with the secretary of state position."

Conway's has gone on a days-long public crusade against the 2012 Republican nominee as Trump weighs several options to be his top diplomat.

After tweeting earlier this week that she'd received messages from supporters voicing their displeasure with Romney, Conway repeated to ABC's Martha Raddatz on Sunday that Romney "went out of his way" to criticize Trump.

The former campaign manager joined a number of Trump confidantes who have taken to the airwaves with their arguments against Romney.

Former House Speaker Newt Gingrich and Fox News host Sean Hannity last week both voiced displeasure at reports that Trump was considering Romney over former New York City Mayor Rudy Giuliani. Though Giuliani was an early frontrunner for the post, Trump was reportedly concerned by potential Republican opposition to Giuliani based on his complicated business ties abroad and his overt public campaigning for the job.

Some observers like former senior advisor to President Barack Obama David Axelrod noted high-profile campaign staffers don't often publicly lobby their former bosses so soon after an election.

Others like Joe Scarborough, who occasionally advises Trump, challenged the president-elect to stand up to his former top aides.

Watch the clip below, via CNN: