That's how Douthat frames the Gingrich and Paul contest in Iowa. He calls Paul "the kind of conservative that Tea Partiers want to believe themselves to be" and Gingrich "the kind of conservative that liberals believe most Tea Partiers to be." His bottom line:

If the town hall crashers and Washington Mall marchers of 2009 settle on a Medicare Part D-supporting, Freddie Mac-advising, Nancy Pelosi-snuggling Washington insider as their not-Romney standard bearer in 2012, then every liberal who ever sneered at the Tea Party will get to say “I told you so.” If Paul wins the caucuses, on the other hand, the movement will keep its honor – but also deliver the Republican nomination gift-wrapped to Mitt Romney.

A couple weeks back, Nate Silver challenged Douthat's final point: 

[Paul] is the only Republican candidate apart from Mr. Romney (and Jon M. Huntsman Jr., who is not competing in Iowa) to overachieve his national numbers in polls of New Hampshire. A one-two punch of winning Iowa and New Hampshire is not impossible for Mr. Paul, and it is hard to know where Mr. Romney might wind up if the field were scrambled in this way.