Pew Survey of May/June 2008 found that:
26% of all American voters consider themselves died in the wool Republicans.
32% considered themselves to be Democrats.
Add the above numbers together and you arrive at only 60%
By far the largest group of voters are those in the remaining forty percent.
Among that forty percent are the people who normally are Republicans but who hated Sarah Palin and turned against McCain and voted for Obama.
If they were enticed by Obama's stance on getting the banks to reform - a stance he offered up repeatedly during his last month of campaigning in Oct 2008 - well, Obama has failed that group with his repeated propping up of the Big Financial Players. So those voters are now among the most avid of the Tea Bag crowd. Their votes are lost to Obama.
Then you have the problem of those who were extremely progressive and who may sit out the election. Obama used the John Edwards/Dennis Kucinich message during the last three weeks of his campaigning in 2008. He failed to deliver on that message. It is possible many of these people will sit out the election.
And apart from the above situations - neither party has done anything much about the fact that the election machinery is extremely hackable. So there is that to consider.
We were told during both the 200 and the 2004 election that the Religious Fundies flocked to the polls and voted for Bush as they find abortion repellent. The numbers did not add up in either of those years - there simply re not that many Religious Fundies out there.
But because of the hackability of voting machines, I wouldn't make any bets about any American election.