With a stronger white majority in 2012 specifically, maybe simply more white turnout at the expense of minority turnout, the map might look like this:
What the electoral map might look like with a stronger white majority (possibly including Hispanic whites):
President Hillary Clinton
President Mitt Romney.
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Overall, Obama faces a very close election in 2012, but still wins 2008. The hardest part for him is defeating Hillary Clinton in the 2008 primaries, this is now harder.