Wikipedia shows state-by-state vote totals for 2004 and 2008, but not yet for 2012, so it's impossible to say if Romney lost previous McCain voters, or if Romney held constant while Obama increased votes in those states.
To put it another way: if Libertarians & others siphoned off a million votes from solid Republican or Democrat states, that would change nothing in the electoral college.
But if some came from critical "swing states", it might make a difference.
2012 Obama vs. Romney by state:
2012 Obama vs. Romney by county:
Compare -- 2008 Obama vs. McCain by county: