Got into this thread late, and haven't read any of it yet, but I offer this--something you'll probably find surprising.
According to some statistics I found somewhere after the 2004 elections, the pattern was this: young voters leaned strongly to the left. Adult voters (i.e. working age) leaned strongly to the right. And then, around retirement age--they suddenly started leaning to the left again!
One could explain this from a person's shifting viewpoints as they get older. Young idealism is replaced by pragmatism is replaced by altruism as you draw nearer to death.
However, there's another, less kind explanation: young people have nothing, so they have nothing to lose. Grown-ups want to protect what they do have from being taxed out from under them. And as people get old, they start noticing those medical programs that are championed mostly by Democrats.
It could be plain old basic selfishness.