Michael Barone is senior political analyst for the Washington Examiner.

In combing through the results of the 2012 election — apparently finally complete, nearly two months after the fact — I continue to find many similarities between 2012 and 2004, and one enormous difference.

Both of the elections involved incumbent presidents with approval ratings hovering around or just under 50 percent facing challengers who were rich men from Massachusetts (though one made his money and the other married it).

In both cases, the challenger and his campaign seemed confident he was going to win — and had reasonable grounds to believe so.

In both elections, the incumbent started running a barrage of negative ads defining the challenger in the spring. And in both elections, the incumbent had at least one spotty debate performance.

In both elections, each candidate concentrated on a more or less fixed list of target states, and in both elections the challenger depended heavily on outside groups’ spending that failed to achieve optimal results.

The popular-vote margins were similar — 51 to 48 percent for George W. Bush in 2004, 51 to 47 percent for Barack Obama in 2012.

The one enormous difference was turnout...