Jonathan writes that "party actors have been very reluctant to line up for any of the surge candidates other than (while he was hot) Rick Perry." Here I want to recall something Jonathan was saying a lot last year. The people who really control public opinion and deliver primary votes in the GOP aren't elected officials. They're people who are basically paid like entertainers -- Rush Limbaugh and Bill O'Reilly. And while it's deeply in the interests of elected officials and staffers that their party win elections, since their career prospects depend on that, entertainers don't have such a strong reason to care. They can happily get behind the unelectable guy who says more exciting things.
So if Gingrich doesn't win big endorsements of any kind from GOP officeholders, who cares? Those aren't the people who deliver votes, anyway. And eventually, it all comes down to votes. Conservative media figures are the relevant party actors here, not New Hampshire congresspeople. They don't have an especially strong reason to give Romney the favorable treatment he'll need to catch up, and they could easily turn Newt's book publicity tour into a presidential nomination.
[Update] Thanks to Andrew Sullivan for the link! I didn't link properly to Jonathan's comments about the entertainers in the GOP media when I first put up this post. For his points on that (which have shaped my understanding of the contemporary GOP) you can look at posts like this: "what Rush and company talk about -- which is driven by what drives ratings and sells books -- then becomes the only thing that conservatives talk about." There's also a great one I can't find about how we haven't ever seen a party like the modern GOP before, where a lot power is in the entertainers' hands rather than the politicians, and how that might result in the GOP doing weird and unprecedented things.