No, even whiter.
If you've been sensing a certain trend while watching the Republican primaries, it turns out you're not wrong. The National Journal ran the numbers
So far, according to exit polls posted on CNN.com, whites have cast at least 90 percent of the votes in every Republican primary except Florida (83 percent) and Arizona (89 percent). In every other state except Michigan (92 percent) and Nevada (90 percent) whites have comprised at least 94 percent of the GOP vote this year. That includes Georgia (94), Virginia (94), Ohio (96), Oklahoma (96), Tennessee (97), South Carolina (98), Massachusetts (98), Iowa (99), New Hampshire (99), and Vermont (99).
By comparison in the 2008 general election, whites cast only 74 percent of the total vote.
So if you're thinking the Republican Party has become almost exclusively a party of white people, you're not wrong. Their primaries are being decided almost exclusively by white Americans, and older white Americans at that:
So far this year, though, voters fifty and older cast at least 70 percent of the Republican ballots in Florida (71) and Nevada (70); at least sixty percent in Massachusetts (64), Georgia (64) Vermont (63), Tennessee (62), Oklahoma (62), South Carolina (61), Virginia (60), Iowa (60) and Michigan (60); and at least 55 percent in Ohio (56), New Hampshire (56), Arizona (55).
The GOP has been trying to keep their nearly-all-white base riled up with race baiting statements (see: Newt versus Juan Williams; Santorum and "blah" people; the entire birther conspiracy theory; the current attempts at generating outrage over Barack Obama once "hugging" some black guy). It may inspire their current members, sure, but there's clearly no long-term future there. Eventually that base is going to start, well, dying.
Long term, Republicans are either going to have to embrace and respect non-white voters or go out of business. While many of their strategists know that, their current base doesn't want any part of it, and that lily white, race-suspicious base is who their candidates are constantly catering to. I'm not sure the Republican leadership really has any control over it.