When people look at the 2008 election they assume that Barack Obama won because he was an exciting new candidate and the Republicans were ridiculously unpopular both with everyone, including Republicans. This was't the whole story. A state by state analysis shows that Obama's performance was better than the 53% of the vote he got. Here's how the 2008 vote looked.
What if the two candidates split the vote in 2008? In order to do that we'd need to deduct 3.3 points from Obama and give them to McCain. So we'll take 3.3% of the votes from Obama in each state and give them to McCain.
Florida, Indiana, Ohio, Virginia, and North Carolina swing over to McCain. Obama still wins, although it's close.This shows that Obama's campaign was effective. They weren't trying to win more votes overall, but trying to win votes in swing states. And they were successful. McCain could rack up all the votes he wanted in Texas, but Obama wasn't concerned with how many he could get in New York. In fact, Obama could've lost the popular vote and still won the election. And not by the half a point Bush lost the election in 2000.
McCain could've won by 1.7 points and still lost. Obama knows how to run an effective campaign, efficiently using his resources. That makes him tougher to beat.