Mike Gerson succinctly lays out part of the case for Chris Christie:

A few thoughts on Mitt Romney’s vice presidential pick: This kind of story is a perfect example of the limits of political reporting.  Speculation is unavoidable, but the number of people with actual knowledge of the selection process is tiny — the candidate, his wife, a few close advisers.  And their political interests lie in the maintenance of secrecy and the cultivation of suspense. Until the announcement, commentary on this subject is essentially content-free. So let me add my own empty conjecture. Romney has a particularly strong stable of prospects. Rob Portman would best fit Romney’s public style and be a major asset in governing.  Tim Pawlenty possesses a genuine blue-collar appeal and would be a grateful, loyal and tireless selection. Paul Ryan is the intellectual leader of the GOP and the most passionate prosecutor of the case against President Obama’s fiscal recklessness.  But the trend of the last few weeks favors Chris Christie. The 2012 election has already proved to be a vicious, negative slugfest.  In the last few weeks, Romney has been accused of committing a felony, avoiding taxes for a decade and contributing to the death of a woman with cancer.  The squeals of various fact-checking outfits go ignored in Chicago. Romney, his family and staff are likely to feel offended and aggrieved.  The question they are probably asking themselves is not: Who is the best vice presidential pick?  Rather, it is: Who is the best wartime vice presidential pick?  Romney needs more than an appealing spokesman.  He needs someone to engage aggressively on his behalf in the daily D-Day this campaign has become.  All four leading vice presidential prospects might play this role.  Christie would clearly play it best.  He is the only one who seems to relish this sort of political conflict. And he has good reason to relish it.  He is a natural, a prodigy, at the art of confrontation. It is one thing to pit Ohio or Minnesota or Wisconsin against the Chicago way.  I predict that Romney will want — and Republicans will welcome — Jersey vs. Chicago.