I could never understand that. One of my big gripes with GWB is that he did nothing in the way of "party-building." The GOP seemed to be winding down during the entire 8 years of the Bush presidency.
The party building peaked in 2002 when he even had blacks and Hispanics supporting him over Sept 11. After that is was damage control. Iraq was his undoing.
He did pull a win in 2004, based on many optimistic Iraq projections, and buying off a couple of key voting groups with borrowed money. But that was only a short term strategy, from 2005-2008 it hit the fan with everything going wrong, one after another with the worst at the end, TARP crisis. There was nothing to build on, he had a 20% base left, if that. He picked a path of no return.