Look at the internals of the polls that have Obama even or up one and you tell me that the dems have the same enthusiasm or more than 2008. Please, in what reality is that going to happen today. You can already see in early voting that Obama does not have the same mojo.
Then take into account when they are polling blue states they get 8-11% telling the pollster they are undecided 5 days out from the election...tell me in what year you have seen that...Uh no, at most this last week, there is 1-3% undecided and you have a lot of people who are not telling pollsters they are either not going to vote or refusing to tell that pollster in a dem state who they are going to vote for. I would be a little worried about those votes if I was a dem.
The next little trick you need to look for is how much they over sample women.
One more thing to really get you to think about momentum....when a presidents party looses big in mid-term elections he almost always goes on to loose.