This is not surprising in the slightest. We only need look back to 1998 to see that the American public has a significant disconnect when it comes to ethics and a president's approval rating.
Clinton had a whopping [link|http://www.cnn.com/ALLPOLITICS/stories/1998/12/20/impeachment.poll/|73% approval rating] in December after the impeachment started. Just months earlier, [link|http://www.cnn.com/ALLPOLITICS/1998/07/29/poll.clinton.lewinsky/|56% believed he lied] and 46% thought (same ref) he actually obstructed justice. The overlap is even greater here than Bush's.
I am really beginning to wonder if, in the current atmosphere of ethical apathy, Nixon could skate away from Watergate. Hell, with the right spin, it might have made him even more popular.