I assume all these pollsters know that although most of the country may want Obama, he won't get those people to vote for him. What i've noticed is that Obama supporters (democratic supporters in general) are very loud about it, but don't show up to the polls at nearly the rate the significantly quieter Mccain voters do.
I was over a friend's house this weekend and there were 10 people there. 3 of them were loudly in support of Obama and it made it seem like everyone was in favor of Obama because no one said they wanted Mccain. I found out at least 4 of them are voting Mccain yet they gave no hint that they were. It's just how things are. Obama needs young voters but they won't go out and vote like everyone anticipates them to do every time. I'm not saying he's not going to win, because the numbers are so far in his favor, but I highly doubt seeing a landslide.