The graph above is from Audacious Epigone:

The interesting question is the gap between Bush’s 2004 performance and McCain’s in 2008 (which was worse than Trump’s in 2016).

The usual explanation is that it has to do with how legal immigrants are desperately devoted to amnesty for illegal immigrants. Of course, McCain and Bush were too, so that doesn’t make all that much sense.

More plausible is that immigrants sensed in Obama, even though he was technically born in an American state (having become one two years before), a fellow non-autochthon.

A third explanation is that the Bush-Rove plan to convert immigrants to GOP supporters by boosting their homeownership through more credulous down payment and income documentation standards was working well in booming late 2004, but had exploded by late 2008. For some reason, however, the economic events of 2008 are not supposed to be related to the political outcome of 2008.