Who are those guys?

It's reported today that Bush's low approval numbers in the polls have rebounded since he gave the interview that was telecast by NBC, not much of a bounce, but still...
He got a big bounce when Saddam was captured, and the biggest bounces on 9/11/01 and in March 2003 when he invaded Iraq.
I can only conclude that there is a large segment of the voting public who swing from disapproval to approval of Bush when he's making war or lying. My baseline question, however, is this: How can a sensible person change his mind about the President of the United States depending on what occurs from day to day? Are 20 percent of us that vacuous?
Don't answer that.