I have noticed one thing in many of the recent polls that no one else seems to have commented on (except in the context of skewed party ID which is a slightly related issue).
In some polls (most notbaly the latest Democracy Corps poll) there is a question at the end asking people asking people how they voted in 2000. IN DC's latest poll it is 51% Bush and 43% Gore (yet Kerry leads Bush 50-47% in the same poll). I have seen simil;ar numbers in other polls.
Of course, as we all know, Gore actually won the popular vote 49-48.5%. So where did all these 2000 Gore voters disappear too? Did they die of old age?
I realize that people sometimes rewrite history about their past voting behaviour (ie: in early 1963, when JFK was very POPULAR, suddenly 60% of Americans claimed to have voted for him and not Nixon!). But that was a situation where the narrow winner of the previous election was extremely popular and cruising to an easy reelection. This is NOT the situation we find ourselves in today. There is NO reason for a 2000 Gore voter to claim to have voted Bush (esp. if the same person now says they will vote for Kerry).
Anyways, I don't know what to make of it, but this tidbit gives me even more confidence that polls may be systematically underestimating Democratic voters.