Mitt Romney continued his "he's a good guy, but..." attack ad series that he began in Iowa against Mike Huckabee with a new "contrast" ad going after John McCain on taxes and immigration in New Hampshire. It begins:

John McCain is an honorable man, but is he the right conservative for the future?

...and ends:

For the future there is a big difference.

Care to guess where Romney's going with the "future" formulation? I like John Dickerson's take:

Taxes and immigration have nothing to do with the future, particularly, but the framing is a not-so-subtle jab at McCain's age. In his closing-argument stump speech, Romney is trying to identify himself with the future. "No one votes for yesterday; they vote for tomorrow," Romney said Thursday in New Hampshire. "Elections are about the future, the future of our families, the future of our country."

Watch it:

John McCain had an impressively rapid response ad ready to go, citing the Union Leader's "The Romney Backlash" and Concord Monitor's "Mitt Romney Should Not Be President" Romney anti-endorsements. For someone who has been as loathe to "go negative" as McCain has been, this ad is a master class in how to attack without seeming to -- use others' words to do it.

Watch it:

So who wins this grudge match? My instinct is McCain. His ad goes right for Romney's throat accusing him of being phony, but the thing is, everyone knows that. It's not exactly news. Romney's ad leaves me a bit cold but does succeed in reminding conservatives of why they don't like McCain (and it gets in that nifty subliminal age rap.) The reason I think McCain might just get the better of Romney by a hair with his ad is that it appeals to a broader group: moderate Republicans and independents who vote in the Republican primary, aka McCain's core constituency. For McCain, this ad isn't about shoring up his conservative credentials (the basis of Romney's attack,) it's about reminding people who the most principled candidate is. McCain further benefits from not having attacked first (it's a response ad) without putting him on defense. Right now Huckabee and Obama are very much on the defensive and it's not an attractive quality in a candidate (I would argue, it may actually be worse than being perceived as a negative campaigner.)

The battle between these ads reveals a major tension that exists between the two candidates fighting for New Hampshire, and I expect, ultimately fighting for the nomination: is it more important to agree with the guy on the issues (Romney) or are integrity and honesty more important in a candidate (McCain.) Right now, the LA Times/Bloomberg poll shows these qualities in a dead heat for 2nd place among likely voters' priorities (10% and 11% respectively.) Interestingly, the top priority listed is "experience/track record" with 16%, which reveals yet another rift in the race: foreign affairs experience would appear to go to McCain while Romney impresses on handling domestic affairs. Romney's continued overall lead in New Hampshire can at least in part be explained by the fact that Americans are more and more concerned about domestic issues as a new AP/Yahoo News poll released on Friday (taken Dec. 14-20) confirmed; the extent to which Benazir Bhutto's assassination will impact this dynamic, of course, is yet to be seen.