Interesting historical chart of the incumbent’s approval rating. Note that sitting president’s below a 50% approval rating 6 months prior to election are considered very vulnerable.
click for larger chart
graphic courtesy of Washington Post
Washington Post-ABC News Poll:
Election 2004 – Post-Democratic Convention
Washington Post-ABC News poll, conducted by telephone July 30-August 1, 2004 among 1,200 randomly selected adults nationwide (including 940 self-identified registered voters).