I think that most people just didn't expect the level of micro-campaigning that the Obama campaign performed. Seriously, the polls had Romney leading independents by double digits, youth turnout was expected to be down, he supposedly caught up with women and had double digit leads among men. Add in the fact that Obama's policies just weren't very popular and he had a bad economy still to deal with. With that kind of formula, any campaign should expect to win, because that is what typically happens. But none of what the polls suggested to happen, didn't happen. Romney only won independents by 4%, he lost women by huge margins as opposed to the single digits, there was a stealth turnout effort with African-Americans, youth turnout didn't drop, etc.