After all, who wants to go vote when they know their candidate is going to lose, possibly by a very wide margin? And who wants to contribute money? Answers: few people and no one, respectively. So, biased pollsters oversample Democrats so their polls will show Obama with a slight advantage and Republicans worry. I just don't understand it. Lesson: don't believe any poll with a partisan sampling advantage of more than D+4 and don't believe a poll that samples "Adults" or even "registered voters". "Likely voters" like Rasmussen samples is the most reliable indicator. Those are the people who will actually be motivated enough to get out and vote.