Realistically he was never more unpopular than the 46% who supported John McCain, 40% at worst.
Most of Bush's popularity was anger amongst his own party, but they were still people who would vote for him against a Democrat. The same thing happened in 2011 when Obama was soundly beating Romney & Co. in head-to-head match ups despite having approval ratings 10 points under. It was angry liberals who would never support a Republican to be elected as an alternative.
So really, where are all these Democrats that like George Bush now?
West Virginia, Kentucky, Tennessee, Arkansas, Louisiana....
