Courtesy of Pollster.
The blue line is the estimated support for the President at each point in time. The gray dots are the individual polls which vary randomly around the estimated support. Each poll will differ from the common trend due to sampling variation, question wording or order among other idiosyncratic factors. The estimated support is based on a local regression which can flexibly fit the trend in the polls.
Each of the smaller charts below plots a red trend line for the polls from the individual pollster. Keep in mind that the size of the don’t know category is a big source of “house effect” variation among pollsters. Those that typically report a higher don’t know percentage will also typically report a slightly lower approval rating.
Should we start a pool on how much lower he’ll go? Can he get into the teens before Decision 2008?
Progressive Intelligencia 
If you’d asked me that question even six months ago I would have said no way, and I still can’t see him dipping into the teens unless he calls for a Draft. The lowest approval rating ever i believe was Richard Nixon at 23% (right before his resignation) so no President (not Carter, not Truman, not the first Bush) has ever dipped quite as low as you’re asking.
We talked earlier about an increase in troops destroying the McCain presidency hopes…well it would also destroy any faith that middle America had in the Republican Party. I can’t see the advisors to the President allow him to cripple the party for multiple elections, and a draft would be the only way he gets below 20%
But then again, this president never ceases to amaze me
I think Truman’s approval got close to that level, but never dipped into the teens. I agree that Bush can’t get into the teens. Probably the only way he gets there is if he gets caught with Cheney under his desk, a la Monica Lewinsky. I’m not sure a draft would even get him that low.
This is from wikipedia:
Presidential job approval ratings were introduced by George Gallup in the late 1930s to gauge public support of the president. George W. Bush holds the record high approval rating of over 85% shortly after the September 11 attacks. The lowest approval rating ever recorded is held by Harry S. Truman, who in February 1952 had an approval rating of 22%. At the same time, Truman’s disapproval rating was 65% (falling 2% from 67% in January 1952). Jimmy Carter is a close second, with approval ratings as low as 26% during his presidency.
Richard M. Nixon had a disapproval rating of 66% just before he resigned. Only four presidents since 1930 have gone their entire term in office without their disapproval rating reaching 50%: John F. Kennedy, Dwight D. Eisenhower, Franklin D. Roosevelt and Gerald Ford.[1]
A popular president, John F. Kennedy’s lowest approval rating was 56%.
Currently, the approval rating of President George W. Bush is estimated by a Newsweek poll to be around 31% as of November 9, 2006.[2]