[T]hough labor unions have a lot of influence within the Democratic Party, they don't have the votes anymore. Just as Republicans are caught between their business-oriented constituencies (who want cheap labor that doesn't talk back) and their grassroots constituencies (who don't like illegal immigration), so too are the Democrats caught between two constituencies of their own [labor and immigrants (broadly defined)].Reynolds may be onto something, and I can't help but look at the past and wonder if a new nativist movement is afoot. I doubt very much any such movement will rely on the same sort of racist, anti-Catholic (for instance) rhetoric of the 19th century. I also expect that those pro-"any"immigrant groups will attempt to portray anti-illegal immigrant groups as the 21st century equivalent of the aforemntioned 19th century nativists (even more than they already have).
The more I think about it, the more this looks like fertile ground for a third party to emerge. Who will it hurt more? The Republicans, or the Democrats? I'm not sure. Perhaps it will shake things up in general.
If Reynold's is correct, than any such party would by definition have a pretty narrow agenda that would probably only appeal to certain sections--both geographically and ideologically--of the population. I'm not knowledgeable enough to define what such a coalition would look like, but I think--and this is no profound insight--that the Southwest would provide a geographical center for any such movement. Given that, perhaps Arizona Congressman J.D. Hayworth (R) could be an attractive candidate to such a movement, though he'd probably run as a Republican.