Will the same voters who voted for Gore and Kerry vote Obama?

A simple question and this touches the race issue a bit. There has been discussion about how some white democrats will not vote for Obama this November. These white democrats are being perceived as racist. My question is this: If you voted for Al Gore in 2000, John Kerry in 2004, shouldn't Obama expect your vote this November? If your answer is anything other than race, please give me policy differences. and uming this means you are voting for McCain, list me some similarities between Gore, Kerry and McCain that made you switch parties.