For decades, 26% has been my gold standard for a President who'd lost the support of all but the hard core. This was Nixon's level of support throughout most of the Watergate year of 1974. Everybody in the world knew Nixon was lying and covering up, except for those Americans who clung to a state of denial due to party loyalty.
So when the three most recent polls all have Bush's approval rating at 26-27%, it's a landmark. Here's the polls, dates that they were in the field, and their Bush approval ratings:
USAT/Gallup - Sept 26-27 - 27%
CBS/NYT - Sept 21-24 - 26%
FOX - Sept 22-23 - 26%
Nixonian. In more ways than mere approval ratings.