HANOVER, New Hampshire — Republican frontrunner Mitt Romney on Tuesday won a key endorsement from popular New Jersey Governor Chris Christie, who said the former Massachusetts governor had the experience to turn around American fortunes.

"America cannot survive another four years of Barack Obama, and Mitt Romney is the man we need to lead America and we need him now," Christie said at a news conference in New Hampshire with Romney.

The endorsement came just hours ahead of a televised debate here among Republicans vying to be their party's pick to challenge Obama in 2012.

Romney has been rising in the polls against his two top challengers, businessman Herman Cain and Texas Governor Rick Perry.

Romney had a huge lead in New Hampshire and a comfortable one in Iowa, the states that hold the first presidential nominating contests next year, according to a survey released Tuesday by MSNBC television and the Marist College Institute for Public Opinion.

Christie, a popular figure with conservative Republicans who was himself considered a potential contender for the party's presidential nomination, took himself out of the running last week.

In announcing for Romney, he cast the contest as one between optimism and division, accusing Obama of playing to the fears of those "who are not doing well and who are scared that the pie of America is only so big."

"I know that Mitt Romney believes that the American pie can be grown bigger and can be an infinite size because of the nature of American ingenuity and effort and character," he said.

He also took a swipe at Perry for a flap in which a pastor who endorsed the Texas governor attacked Romney's Mormon religion as a cult.

"I think that any campaign that associates itself with that type of conduct is beneath the office of president of the United States," Christie said.

Photo credit: Gage Skidmore