The Republican Party has become the party of the white majority of all income levels. Nevertheless, whites of different income levels vote Republican for different reasons.
The divide that really matters, the one that demographically dooms the GOP in its present formation, is not ethnic, or even class, but generational. See the Pew Political Typology 2011. Nearly half the GOP's base is now the "Staunch Conservatives," which is also the oldest group (and the whitest, BTW) -- and, when they die off, they will not be replaced in commensurate numbers. Their children and grandchildren may be conservative in some sense, but not in anything like the same sense. Because the Staunch Conservatives' politics and general world-view are not a result of people growing more conservative as they grow older (actually, people tend to grow more liberal as they age), but a matter of generational culture, of having been shaped by a world that no longer exists.
