As best I recall, he was always negative on the Republicans' chances, then right at the end started to shift his ground so he would be closer to reality.
An old sports adage is "you don't beat sumptin' wit nutin'" and the Dems got nutin. We may not be happy with big government spending, no border control, and Medicare drugs, but any Republican/conservative in his right mind knows that if the Dems get ahold of national security, it will be (to quote "Team America, World Police") "9/11 times a hundred." And THAT won't be funny.
Or, perhaps he was picking up on a late surge that favored Republicans. Most observers believe this is what happened thanks to superior organization, better use of money, and a very effective get out the vote effort. Do you think this is likely to repeat in 2006?