Nate Silver has an interesting post arguing that Chris Christie managed to become a darling of the conservatives without being as conservative as they think he is. He "supported the assault weapons ban and opposed concealed carry laws." He "stated explicitly that global warming was real and manmade." He "stated [in 2008] that 'being in this country without proper documentation is not a crime.'” He has "no issue with same-sex couples sharing contractual rights,” i.e., civil unions, though he does oppose abortion rights and same-sex marriage. He's soft on the "ground zero" mosque (which is actually a couple of blocks away). He declined to challenge Obamacare in court. And he actually put out an Obama-friendly ad during his 2009 gubernatorial campaign.
All this really says, Silver points out, is that Christie is about as conservative as you can get away with being when you're governor of New Jersey. This is, after all, a state so liberal that you aren't even allowed to pump your own gas, lest an attendant be put out of work. But that suggests his natural rival isn't Rick Perry; it's Mitt Romney, whose problem is kind of similar. So if your reason for wanting another candidate in the race is you don't like Romney, root for Christie to get in so he and Romney can split the moderate vote and throw the nomination to Perry. But if your reason for wanting another candidate in the race is you don't like Perry, then you should root against Christie jumping in. Silver's analysis is somewhat more nuanced than my summary here, but that I think is where it takes you.
Update. Dan Amira says the same thing on New York magazine's Web site ("Five Things Republican Voters Would Hate About Chris Christie"). At Mother Jones's Web site, Kevin Drum is sold. But the Weekly Standard still seems pretty excited about a Christie run. All this speculation seems to have worked wonders on Christie's in-state favorability rating.