New Jersey Gov. Chris Christie is stumping for Mitt Romney in Iowa, trying to boost Romney's campaign in the face of a surge by Newt Gingrich.

Christie, who weighed a presidential run himself before deciding against it in October, pulled no punches in defending Romney against his critics, many of whom say the former Massachusetts governor isn't conservative enough or has changed his positions too many times.

If you're looking for a candidate who agrees with you on everything, buy a mirror, Christie told a crowd of about 100 Republicans in West Des Moines, Iowa, on Wednesday. I'm out here to tell you that I'm supporting him because I believe he's the best qualified person to be president, and I believe he's the only Republican who can win.

Aside from is he electable, the real question voters should ask is this, Christie said: Is this the kind of person that is always going to make me proud in the Oval Office, and I never have to worry whether they'll embarrass America, that I never have to worry will do something that will make me ashamed?

Emphasizes Romney's Family-Orientation

He called Romney that candidate and told an anecdote about Romney's visit to Christie's New Jersey home to illustrate his character.

He spent as much time talking to my children -- I have four of them, between 8 and 18 -- [as] he spent talking to me and Mary Pat, Christie said. Politicians can be taught to fake a lot of things. You can't fake that. This is someone who I've come to know has an extraordinary heart. He loves his wife, he loves his children and he has absolutely no hesitation in showing that affection openly. Now, that's not what you see on TV all the time, but I sat in my back yard for two and a half hours and watched him talk to my children.

Christie did not mention any of Romney's opponents by name, but the contrasts he made were clear. The focus on Romney's love for his family, for instance, stood in unspoken contrast to Gingrich's well-publicized extramarital affairs -- something Romney himself took advantage of in a recent Iowa TV ad that highlighted the fact that he has been married to the same woman for 42 years.

Christie also said that having Barack Obama in the White House should have taught Republicans the dangers of electing a president who has no executive experience.

We've seen for the last three years what it means when we have a legislator as president, he said. I have nothing against legislators ... but they've never run anything. They don't know how to run something, and we have seen what it's like to have someone in office who doesn't have the first idea of how to use executive power or how to exert real leadership.

It is more common for modern presidents to come from executive backgrounds like governorships than from legislative backgrounds, although congressional leadership experience -- like Gingrich's four years as speaker of the House -- can sometimes make up for a lack of executive experience. Lyndon B. Johnson, for instance, was a lifelong legislator before he became vice president, but he served as Senate majority leader for six years and as minority leader before that.

But Christie said at the West Des Moines rally that he was not worried about Gingrich's rise in the polls.

Lots of people have surged in the polls out here, he said. I wasn't concerned about Michele Bachmann or Herman Cain or Rick Perry. Mitt Romney is the steady, mature leader we need for our party and our country.