The Republicans will not be able to make illegal immigration the wedge issue that gay marriage was in 2004 for one reason: they themselves are divided over it. Almost every Republican supported state-wide refferendums on banning homosexual marriage. But the Republican Party has pro-illegal immigration and anti-illegal immigration factions.
The pro-illegal faction is primarily the corporatocracy elites who spout the bullshit of how illegals are doing jobs that others won't do. They tell us that if we enforce the laws and tighen our borders, that our lettice will be expensive and our consumer lifestyle will be DOOOOOOMED! The bigwigs in the Cato Insitute, and Grover Norquist himself want a libertarian-style immigration policy because it helps in their efforts towards union-busting a driving down wages. Bush wants a guest worker program that will create an underclass of low-skilled workers that can't vote or can't unionize.
The anti-illegal faction is strongly opposed to the Bush policy. They're correct in opposing illegal immigration, but they do so out of xenophobia, while progressives who oppose it did it in the name of economic fairness for American citizens regardless of race, and for the unions and the right of organization. I would say that the majority of rank and fiel conservatives who live in red states and blue state alike are opposed to illegal immigration. The "Country Club Republicans," are some of the same elites that want to break the backs of working stiffs, some of whom vote Republican because of the social issues or national security issues.
This DU thread on Free Republic's reaction to the Bushs proposal is telling:
http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=364x764341Ultimately, I believe that the pro-illegal faction will win out, either by compromsing with the xenophobes in creating a bill that will have loopholes, or they will outright kill it.