I believe that the polls are missing a potentially large demographic. Everyone who has graduated from college since 2001. Their were, "1,244,000 bachelor's degrees conferred in 2000-01". That is about four million people who were in college when the twin towers were struck. I think this demographic is very important because of the prominence of 9/11 in this demographic's mind and the several problems in measuring the sentiment of this group.
The problem with polling this group are:
They may not show up on Most likely voters polls. College students are not know for their voter turn out, and this group has not had a chance to vote in a national election since 9/11.
They address may not be included on polls as much as other voters who have a long standing address and a listed phone number. Their contact info might be present to a lesser extent. Most probably do not own homes and probably live with parents or in apartments. Some may not have home phones. I have a cell phone, and do not have a home phone.
Once their contact information was included they might stayed below the radar of the polling agencies. How many 22-26 year olds are home when the pollers call. I would guess to a lesser extent then the 30 year old with kids.
I think the polls are probably trying to poll this demographic comparable to percentage that voted in the 2000 election. If 10 percent more of this demographic turns out, that is about 400,000 voters. If this demographic turns out in force, seventy percent, that is about 800,000 more votes being cast. Enough to decide the election, maybe.