What's different is that the other surges united most of the anti-Romney voters. This one is doing that, too, but it is also cutting into Romney support.
My impression had always been that the Perry surge initially involved some Romney supporters (Romney's support fell from about 20% in most polls to the mid-teens toward the end of August just after Perry's entry).
That said, it's interesting that Gingrich has a kind of appeal that goes beyond what I guess is being called the Tea Party portion of the Republican electorate. Both Cain and Bachmann clearly did not.
