The graph is from Charles Franklin at Polls and Votes. Everyone is talking about Gingrich, now because of the Manchester Union-Leader endorsement. See Nate Silver's analysis.
But I'm especially curious about Ron Paul. Why are his numbers dropping? Although it's true that he hasn't gotten much media coverage, it's also true that media coverage can be as much bane as blessing (see: Cain, Herman). And Paul was relatively familiar to most Republican voters, which suggests that their attitudes aren't changing simply because they didn't know who he was and now they do.
Or maybe they didn't really know who he was-despite his 2008 campaign-and now his breaks with Republican orthodoxy are now more visible. But what would drive that impression? Again, it's not like he's getting a lot of media coverage. Or time to speak in the GOP debates.
Maybe I'm missing something subtle. Or something obvious. I just wouldn't have expected Paul's numbers to move that much.
