Since 1988, the largest party ID differential for any election - that includes 2 Clinton wins, the Rep takeover in '94, the Dem takeover in '06 - has been Dem +4 in '06. Every election Dems think THIS will be the year that all those winos, homeless, and college students are going to vote, and it hasn't happened yet. Some day it may, but I have no reason to believe that this will be the year. Remember, all those newly registered voters were unregistered for a reason - THEY DON'T VOTE!
If turnouts are comparable to '04, and McCain gets > Bush's percentage of Indies (48%) - which has been his plan all along - then regardless of the historic significance, this should be a Dem heartbreaker again - only funnier! Actually, what Obama has to realistically hope for is that he is seen as inevitable; hence, the phony poll demographics. This sways the herd mentality of the "Independents" (Ironic isn't it?) toward the preordained candidate.
Remember, many Independents/Moderates just want to say that they voted for the winner as it confirms their disengaged selfabsorption.