Matt Steinglass is half-right when he says this:

Republicans aren’t concocting grand strategies based on John Judis and Ruy Teixeira’s thesis that they face demographic doom, because they don’t believe that thesis. I think most Republicans actually don’t think that their hard-line anti-immigration stance ought to be costing them the Hispanic vote. As far as they’re concerned it’s the right policy, and Hispanics ought to be able to see that.

I agree that most Republicans don’t believe this thesis when it is presented to them. Many Republicans are scarcely aware of this argument in the first place, but they are far more likely to believe that America is and will continue to be a “center-right nation.” When asked to provide evidence for this view, they will probably invoke polling data on ideological self-identification, and if that isn’t enough they will point to the 2010 midterms. Many Republicans view the composition of the 2010 electorate as proof of the resilience of the Republican coalition after the aberrations of 2006 and 2008. 2012 will likely be a disillusioning election for them.

Most restrictionist and enforcement-first Republicans assume that most Hispanic voters are not likely to vote for the GOP for a number of reasons besides immigration policy. This may be a convenient assumption, but it also happens to be true. Whether or not stricter immigration policy “ought” to be alienating Hispanic voters, the assumption is that most Hispanic voters already disagree with the GOP on too many other areas of policy*. Liberalizing the party’s position on immigration would simply be unimaginative pandering that would also fail to win over many voters, and in the process it would cause significant disaffection among the party’s reliable voters. Bush, Perry, et al. lost the intra-party fight on immigration on policy and political grounds, and for once the party’s corporate backers did not get their way. Immigration restrictionists see an amnesty or semi-amnesty policy as the thing that will hasten the current GOP’s political demise. Restrictionists assume that the policy concession that is being promoted as the way to boost Republicans’ political fortunes will instead be the fast track to near-permanent minority status, and judging from the effects of the last amnesty bill they aren’t wrong.

* I should add that thinking about this in terms of policy disagreements doesn’t take account of the role of identity politics in drawing/pushing Hispanic voters away from Republican candidates, which is probably even more important in determining voting patterns.