Demographics. Colorado voters are unusually young and white collar, areas where Obama does better than the average Democrat. They also have a growing Hispanic population. Similar story in Virginia.
In contrast, Pennsylvania and Michigan have older, blue collar populations, and as a result McCain is doing better there.
Sheesh, its scary that it is even close. But on the bright side, if we pick up Wisconsin and take Penn; it’s over for socialism this election cycle.
CO and VA, like MI and PA, still have strong traditional voting patterns that we should remember.