The campaignerati like to say that states are the only things that matters, so you should ignore national polling. That's a little bit right but mostly wrong. As the nation moves, so do the states, which means that national polls mean a lot even when the individual contests are fought at the state level.
That said, the latest polls show Romney finally making a serious surge at the national level. As the RCP summary below shows, the three national polls taken after the New Hampshire primary show Romney with 34%, 37%, and 40% of the vote. That means he's finally cracked that 25% barrier that seemed to be his ceiling for so long. For good or ill, he'll be the GOP nominee unless he somehow contrives to completely crash and burn in South Carolina. It's all over but the shouting.
UPDATE: You want an alternative story just to keep things interesting? Fine. Perry is already toast and Ron Paul doesn't really matter. If Santorum does really well in South Carolina and Gingrich decides to drop out, leaving it a clear two-person race, I could see just a sliver of hope for Santorum. But this is the best case I can think of, and even at that it's just a sliver. At this point, Romney would have to screw up pretty spectacularly to lose.