President Obama, always the favorite punching bag of Republicans at a presidential debates, took a few new -- and surprising --  hits last night in North Charleston.

Republican candidates Sen. Ted Cruz of Texas and Gov. Chris Christie of New Jersey ratcheted up the anti-Obama rhetoric to a more personal level.

Christie debuted a new line, saying he would "kick" Obama's "rear end" out of the White House come 2017.

"Mr. President, we're not against you. We're against your policies," Christie said. "The American people have rejected your agenda and now you're trying to go around it. That's not right. It's not constitutional. And we are going to kick your rear end out of the White House come this fall."

Cruz followed up with his own insult, calling Obama a "child" -- which appeared to borrow from one of Christie's favorite lines that labels Obama a "petulant child."

"Donald is right that China is running over President Obama like he is a child. President Obama is not protecting American workers and we are getting hammered," Cruz said.

By contrast, the attacks on Hillary Clinton, the Democratic candidate most Republicans seem eager to go up against, were relatively mild. Probably the toughest invective against Clinton was that she would be "a third term of Barack Obama's leadership."

The escalating rhetoric against Obama could, on the one hand, be seen as a natural consequence of a campaign in which virtually nothing is off limits.

Or perhaps, it is just another example of the political and personal discord often reserved for Obama -- which perhaps began with South Carolina Rep. Joe Wilson's headline grabbing "You Lie!" outburst during Obama's joint congressional address in September 2009.

Christie, in particular, has deployed his famously blunt personality to score points against Obama. And he continued to hammer Obama for what he has described as his "lawlessness."

"This is a guy who just believes that law enforcement are the bad guys," Christie said on Thursday night.