TPM links to this incredible 2 pager at CBS that shows that the Romney campaign was absolutely confident that they were going to win the election. The second page has what they think are the three major miscalculations:

1. They "unskewed" the polls (even their own internals) and assumed low minority turnout
2. They didn't understand or believe what was widely known about Republicans identifying themselves as Independents in polls
3. They kept faith in the "undecideds always break for the challenger" rule that hasn't been true recently (see Nate Silver, ofc).

TPM has a great chart illustrating the party identification issue and the post on this is a good follow-up anyway. Josh Marshall has trouble even buying the veracity of the CBS article.

Points 2 and 3 may be technical miscalculations, although while i could see letting those items give yourself hope when the polling is against you, it's a far cry from that to being confident in a win, as the CBS article predicts. But the first point is really just believing your own propaganda. They sold the message that Obama was a failure and had disappointed even his own supporters for so long that they couldn't believe anyone show up to vote for him. In fact Obama increased his turnout in key areas whereas Romney didn't get all of McCain's votes.

(Maybe they just read too many liberal blogs. We bitch and moan a lot, but Obama's approval ratings have always remained high. There aren't enough disgruntled bloggers to change that, and most of us probably come along in the end anyway.)

The math showed a comfortable victory for Obama. Even the misinformed pundits predicted at best a nail biter. I just don't understand how you get to "I don't think there was one person who saw this coming."