Protesters crashed the former governor's campaign rally at an Exeter-area high school, chanting "Mitt Kills Jobs." and other insults. The shouts could be heard even after some of them were escorted out of the event.
Romney was polite with the protesters as he spoke, saying he respected their views but wished they would be more polite.
However, Christie didn't hold back when it was his turn to address the packed high school gymnasium.
When a heckler yelled, "Christie kills jobs," Christie was ready with a response - New Jersey style.
"Really?" Christie replied. "Something may go down tonight but it's not going to be jobs, sweetheart."
Christie, a potential vice presidential running mate should Romney win the Republican presidential nomination, has emerged as one of Romney's top surrogates on the campaign.
He deftly turned the protesters' complaints into criticism against Democratic President Barack Obama, who will face Romney or another Republican in next November's election.
Obama has "encouraged these people to be angry at Mitt and angry at me because we stand up for what we believe in," he said.
"Mr. President, you're up there in the family quarters of the White House, put your feet up and don't worry about it. Mitt Romney is going to bring people together," said Christie.
The crowd roared its approval.
"He handled them just the way I would expect him too, an intellectual beat-down," said Mike Gianino, 51, of Newton, New Hampshire. "I think Christie is just the right amount of punch."
The Romney event was one of many GOP candidate events planned this week, as the candidates race to gather supporters before Tuesday's primary.
Knocking Romney off his perch before Tuesday won't be easy.
He has spent the better part of two years essentially adopting the state as his own and now holds a comfortable lead in pre-primary polls as his rivals essentially battle for second place.
Roughly $5 million has been spent on TV ads in the state by candidates and political action committees aligned with them -- called super PACS -- with most of the money coming from a pro-Jon Huntsman group and Texas Rep. Ron Paul. Romney has spent roughly $1 million.
The former Massachusetts governor won the Iowa caucuses last week by a scant eight votes over Santorum.
Huntsman, the former Utah governor, skipped Iowa in hopes of a breakout showing in New Hampshire.
South Carolina comes next, on Jan. 21, the first Southern state to hold a primary. Perry is skipping New Hampshire to campaign full-time in South Carolina in hopes of reviving his candidacy.
The Associated Press and Reuters contributed to this report.