Losing His Religion
Because of the impeachment and Lewinski issues, Gore decided to keep Clinton at arm's length, depriving himself of a major fundraiser and an effective advocate. He still won, of course, but maybe the extra votes may have made it harder for the Republicans to steal.
McCain is running hard AWAY from the Bush legacy and the base is abandoning him in droves. The fact is that the hardcore Thug faithful see Bush as a religious icon, like they do Reagan.
Choosing to run against Bush, as unbelievable as it is, is atomizing his base.