Donald Trump discusses Jeb Bush on CNN. CNN/screenshot Real-estate magnate Donald Trump has been firing attacks at former Florida Gov. Jeb Bush (R) throughout the day Monday, a day before the all-important New Hampshire presidential primary.

In at least five separate media interviews, several campaign events, and on Twitter, Trump has railed against Bush, one of his GOP primary rivals.

Among other things, Trump has called Bush an "embarrassment to his family" and compared him to a "little sheep" at the Republican presidential debates.

"He's a desperate person. … He's a desperate person. He's a sad and he's a pathetic person," Trump said on CNN. "He doesn't even use his last name in his ads. He's a sad person who has gone absolutely crazy. I mean, this guy is a nervous wreck. I've never seen anything like it."

In the same interview, Trump also said:

The guy's got a failed campaign. He's a nervous wreck. He's probably going to be the last of the governors [who are running for president], I would say. Certainly he's the least talented of the governors. And he's done very poorly in the debates. … I always put him down on the dais and he goes away like a little sheep.

Trump was reacting to Bush throwing a number of barbs at him earlier in the day. Bush has been Trump's chief campaign-trail critic, and the Republican front-runner has never hesitated to return fire even as a number of other rivals have surged past Bush in the polls.

Donald Trump on MSNBC's "Morning Joe." "Morning Joe"/screenshot

But Trump went out of his way to go after Bush on Monday. At a campaign event in Salem, New Hampshire, Trump responded to multiple unrelated questions by going after the former Florida governor.

"He's on every show: 'Donald Trump said this. Donald Trump said that,'" Trump said after a man asked about the Clintons and political corruption. "And then he said, 'See, I'm the only one taking on Donald Trump. I'm not afraid of Donald Trump.' He's like a child. He's like a spoiled child. He spent $110 million on a campaign and he's nowhere."

At other points in the event, Trump called Bush "an example of a real stiff," weak on various issues, and "not a smart man." Trump also ripped into Bush during two separate MSNBC interviews, a CNBC interview, and on a Boston-based sports-radio station.

Reached for comment on the onslaught, Bush spokesman Tim Miller told Business Insider that Trump was acting like a typical bully.

"Bullies don't like to be attacked so they lash out," Miller said. "It is the sign of a weak and insecure person."

Bush and Trump also went back and forth on Twitter: