I don't know if we've reached, or are reaching a Tipping Point where the Republican majority begins to disintegrate, but I think there are a number of reasons to wonder where the conservative movement goes from here, especially if the conservative chatter after last night's prez address is at all reflective of the movement's strains.
As Glenn Greenwald suggests, the Republican Party breakdown on immigration, at this particular time, probably owes a lot to the fact that the war in Iraq has failed to live up to its billing; it's producing neither clear-cut military or moral victories.
But as Barbara at Mahablog discusses, there's certainly more going on, above as well as beneath the surface, here than immigration politics and the war in Iraq. The last four decades have represented what political scientists refer to as a secular realignment; a realignment in party control that develops over a period of time, as opposed to the type of party realignments that stems from a crisis event (i.e. the Great Depression). That gradual-ness has allowed the party elite to draw ever widening groups of the electorate into its fold, largely based on symbolic and rhetorical gestures (the flag, religious values, etc) without signficantly altering the basic structure of American society and government and without therefore turning off essential components of the political middle. The downside for the Republican Party is that its more baser elements are tired of the slow process of change and now want more visible and substantive results. The party's further downside is that to implement the changes demanded by its baser elements would be infeasible.
The appointment of two conservative justices to the Surpreme Court, and the passage in South Dakota of an abortion-criminalization law highlight the risk involved in moving the party further to the right on social issues. It was one thing to call abortion murder when conservatives weren't running all three branches of government. It's another thing alltogether to implement the logical extensions of the abortion-is-murder argument and criminalize abortion providers and abortion consumers.
Taxes represent another problematic front. Cutting government to the bone was a lot easier spoken of in theory, from outside the halls of power, than it was once the party was in charge of government. Even though conservatives were more than willing to let most dimensions of federal capabilities and authority whither on the vine (like FEMA), today's conservative movement actually has little to do with the frequent calls for "smaller government" that it's rhetoricians have been broadcasting at least since the Reagan era. Conservatives very much want big government to do things--like "enforce our borders" and eliminate the opposition (us liberals). Those types of things tend to require government employees and structure of some kind, which all in turn, require money. Tax money. The marginal utility to be derived from the "tax cuts today, tomorrow, and forever" part of the Republican Party platform is all but used up.
Finally, the "war on terror" rhetoric is also wearing thin. Wars are exciting for a certain class of the conservative movement. But unfortunately for this class, they are finding out that war is a pretty limited instrument, especially when it's discovered that it involves material and physical sacrifice to implement. And this most conservatives, comfortable in their homes with their keyboards, are unwilling to follow through on.
This reluctance to put its money where its mouth is, is probably the decisive factor preventing (at least for now) the full flowering of a fascist party in the U.S. Conservatives talk tough, they may make death threats to celebrities or schoolchildren, they may call for eliminating liberals from their audiences, from the nation's campuses, and from society, but in the final analysis, the conservative movement lacks the Will to implement its dreams. It is cowardly.
Put simply, the conservative movement is at, or at least very near, a breaking point between its rhetorical and symbolic goals on the one hand, and the policy choices needed to implement its rhetoric on the other.