Donald Trump: Jeb Bush is 'dumb as a rock'

Donald Trump has singled out GOP rival Jeb Bush for criticism plenty of times -- and he's at it again. In a series of tweets Friday, Trump called his 2016 rival Jeb Bush "dumb as a rock" and said his campaign was incompetent.

Bush didn't take the insult lying down. According to CNN the GOP contender told a town hall in New Hampshire Saturday morning, "Just one other thing -- I gotta get this off my chest -- Donald Trump is a jerk."

Bush, for his part, has been giving as much as he's been getting on Twitter. He's even compared Trump's ISIS strategy to that of Hillary Clinton's.

But it's not just Twitter where Bush and Trump butt heads. Bush has been one of the few Republican candidates willing to go after Trump in the debates.

And Bush has a lot of anti-Trump ads on his official YouTube channel as well. He has even gone so far as to call Trump the "chaos candidate."

This recent wave of attacks on Trump might come from Bush's performance in the last debate.

Trump, of course, has never been shy about attacking Bush. And he's gotten good at using social media to do so.

But of course, this is a presidential election so some mudslinging is to be expected. Hey, at least it's kind of entertaining this time around.

See Donald Trump through the years:

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