it's because Kerry failed to contest him on the dominant issue in the campaign, the war in Iraq. This Time magazine essay calls Kerry's position on the war as a straitjacket, and rightly so. Kerry has been wholly complicit in Bush's mishandling of the war, silent about the ab-graib prison scandal, silent about the ongoing killing, about Halliburton's defalcations, about even the on-again, off-again conduct of military operations.
I'm miserable, watching Kerry give away all these points while being hammered for his war record. I'm actually angry at Kerry for misguaging the issues so grossly.