RNC Chair Reince Priebus was reportedly “apoplectic” over Trump’s bucking the party line by refusing to back House Speaker Paul Ryan (R-WI) or Sen. John McCain (R-AZ) for re-election and called several of Trump’s staffers to voice his discontent, according to NBC's Katy Tur.

A longtime ally of top Trump staffer Paul Manafort also told CNBC’s John Harwood that Manafort is “not challenging Trump anymore” and is “mailing it in,” while the campaign staff is “suicidal."

Top staffers "feel like they are wasting their time," on Trump's campaign, CNN reported.

NBC News’ Peter Alexander tweeted that an anonymous source confirmed “it’s all true” about Harwood’s reporting and that the situation is “way worse than people realize.”

Jason Miller, a spokesman for the campaign, called Harwood's reporting on Manafort "completely erroneous."

"The idea that Paul Manafort is mailing it in is completely erroneous," Miller said in a statement to CNN. "Our campaign just finished up our strongest month of fundraising to date, we're adding talented and experienced staffers on a daily basis and Mr. Trump's turning out bigger, more enthusiastic crowds than Hillary Clinton ever could."

This post has been updated.