TRUMP: 'Crazy' and 'very dumb' Mika Brzezinski had a 'mental breakdown' on 'Morning Joe'

Donald Trump slammed the co-host of MSNBC's "Morning Joe" in a tweet Friday morning, as the show has started openly taunting the Republican presidential nominee in recent days.

"Just heard that crazy and very dumb @morningmika had a mental breakdown while talking about me on the low ratings @Morning_Joe," Trump tweeted. "Joe a mess!"

It wasn't immediately clear to what Trump was referring, but last week Mika Brzezinski railed against Trump for calling Democratic presidential nominee Hillary Clinton a "bigot."

"We were just talking off-set, and I have to say it," Brzezinski said. "Donald Trump, you have no idea what your words mean. You have no idea. You have no idea what your words mean."

She continued: "I can't pretend and sort of try and cover this fairly and put it in the veil of objectivity. This is wrong. You have no idea what your words mean and what you're doing to this country."

"Morning Joe" has been increasingly critical in its coverage of Trump. Earlier this week, show host Joe Scarborough started calling Trump "Amnesty Don," using Trump's tendency to come up with nicknames for his opponents to mock the candidate's softening on his signature issue - immigration.

Scarborough followed the new nickname with a music video that chided everything from Trump's appearance to his immigration policies.