I think the race is close, but the percentages are probably fixed. In short, Obama will likely win because certain groups would never not vote for him. Most women, the huge majority of blacks, Hispanics (other than Cubans) and union voters will simply vote for him because they won't vote for a Republican. The Republicans have their own base that will not budge either. There are independents, but they have probably already decided too, or are staying home.
In short, the Democratic base is likely to be slightly bigger than the Republican one, so the Democrats will win, but the actual percentages will be close in an absolute sense
Which really means it will depend on where the "majority" comes from. Remember, in this country we do NOT vote for president - we vote for electors who vote for president (the Electoral College). A "majority" does not guarantee a win.