Rick Santorum just put out the anti-Romney ad Gingrich should've come out with back in Iowa. It's a powerful argument tying Mitt Romney to Barack Obama:

Now that's some good negative campaignin'. There's none of that Bain stuff that Gingrich has been parading around—those anti-Bain attacks will play better in the general, when the race is not strictly about defeating Obama. There's just good old-fashioned conservative fear-mongering and liberal-bashing. Too bad it's probably too late, with the media all but declaring Romney the nominee.