AJ-Strata has an excellent post on why the Congressional GOP is lagging McCain.
The tone the right has taken on immigration has been shrill, declaring those who did not toe a hard line traitors repeatedly, as well as enemies of the Republic (Paul J. Cella is one of the more easily found ones, but you can see similar sentiments in some comments on threads at Free Republic). As I posted elsewhere, such comments have been counter-productive, to put it mildly, and arguably, destructive to the Republican coalition. Some of the comments, quite frankly, would only have been resolvable via the Code Duello.
The hard-liners on immigration have been akin to the people crying about global warming - with practically no proof for their dire predictions, and their response, is much like those of the global warming believers to critics, as described by Michael Crichton.
Some of this rhetoric borders on the fringes as well. In the age of Google, it is easy to find. It's why the "dirty pool" MacRanger describes can stick, as well, even when the specifics are false. Just glance at the immigration threads at FreeRepublic.com, or comments at Townhall (particularly those directed at supporters of President Bush on immigration, like Linda Chavez or Ruben Navarrette), and you can see just why the dirty pool works. The lies are believable.
Contrary to what Mac wants to believe, the MS-1 loss, as well as Hastert's seat, indicates that conservatives have lost touch with America in some respects. I can't speak for anyone else, but who wants to vote for someone who views them as a traitor over a disagreement - much less work with them?
Perhaps MacRanger can answer that question. Because the Congressional GOP needs to either answer that question - or they need to mend fences with the moderates they have been working so hard to alienate.