Story highlights Donald Trump and Ted Cruz are going after each other on Twitter

The pair sent back and forth negative messages over the weekend

(CNN) Donald Trump and Ted Cruz sparred online Sunday for the third straight day, with Trump attacking his rival who has surged past him in the latest Iowa polls and Cruz deflecting the barbs with humor.

As the Texas senator gains ground over the billionaire businessman, Trump used a "Fox News Sunday" appearance to refer Cruz as "a little bit of a maniac."

"When you look at the way he's dealt with the Senate, where he goes in there, like a, you know, frankly like a little bit of a maniac, you're never going to get things done that way," Trump said, a reference to Cruz's habit of bucking even his own party leader's wishes while serving in Congress.

Cruz used Twitter to respond to Trump's latest volley hours later, writing, "In honor of my friend @realDonaldTrump and good-hearted maniacs everywhere..." with a link to a YouTube video of the song "Maniac" from the movie "Flashdance."