You say "he's already clinched it, what a stupid bet" but that doesn't take into account the following: he's a prostate cancer survivor, is 60 years old, and may have other unknown health problems (I suspect he has agromeglia, the same disease that Lincoln is said to have had). So you can get maybe 30-1 or so (at Tradesports) that "health issues" will force Kerry out of the race before the Democratic convention.