One of the most frequent searches of PoliticalArithmetik is some variation on how low can approval of President Bush go. President Truman holds the all time low record, at 22%, and the comparison of Bush to Truman comes up a lot. So let's take a look at second term presidents who had generally low approval ratings. (That leaves out Eisenhower, Reagan and Clinton, plus the ones who never got a second term.)
It turns out the Bush-Truman comparison is a pretty good one in terms of both trends and levels of approval. Truman's bounces are similar to those of Bush and the current level of approval and its trend are quite close. In comparison, Johnson did better throughout his war, while Nixon sank lower and quicker as Watergate came to dominate public perceptions.
This doesn't mean that Bush will necessarily challenge Truman's lows, however. Throughout his presidency, Bush has maintained a considerably greater loyalty among Republicans than Truman did among Democrats. I wrote about this earlier here. At his low point, Truman was supported by less than half of all Democrats. Bush has never fallen below 70% approval among Republicans in Gallup polls. (He has been lower in other organization's polling, though not by a lot.) His support among Republicans in Gallup polls taken since January 1, 2007 are in order 79, 71, 76, 78, 76, and 70, for an average of 75.0%. By comparison, in the same period of 2005 Republican approval was consistently in the low 90s, averaging 91.1%. For the same period in 2006 it was mostly in the 80s, averaging 82.1%. So while Republican support has eroded significantly in the last two years, it remains well above Truman's lows among Democrats.
I don't think current trends alone are good predictors of future approval. Circumstances, events and presidential behavior drive approval, not a blind trend. So things could move up or down depending. But that said the comparison of Bush and Truman's approval trajectories is striking.
(Thanks to Phil Klinkner for provoking me to look at this.)
P.S. Some argue that being the "new Truman" is a good thing-- that history will judge President Bush much more favorably than do his contemporaries, just as has happened with Truman. I have no view on this aspect of Bush as the New Truman. I'm only concerned with the approval ratings here.
Cross-posted at Political Arithmetik.