36% (Pew)
The Chimp in Winter

From the Pew Research Center:

President George W. Bush's approval ratings have fallen to another new low, amid a growing focus on alleged ethical lapses in his administration. Just 36% now believe that Bush has lived up to his campaign pledge to restore integrity to the White House.
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Bush's current 36% job approval rating is the lowest of his presidency, down from 40% in late October and 50% at the start of the year. This decline reflects a souring of opinion among independents just 29% approve of the president's job performance today, compared with 47% at the start of the year. Democratic evaluations have been both stable and overwhelmingly negative over the course of the year.

However, Bush is also now facing a significant loss of support within his own party particularly among moderate Republicans. Overall, the proportion of Republicans who approve of Bush's job in office has dropped from 89% just after the 2004 election to 77% today.

The most significant turn in Republican support occurred in late summer among the party's moderates and liberals, who make up 37% of the GOP. Between July and the end of September, the percentage of moderate and liberal Republicans who approved of the president's job performance fell from 81% to 60%. While there has been some rebound since this post-Katrina low, currently 66% of moderate and liberal Republicans approve, while 29% disapprove of the president's job in office.