Peaking too early is also a problem. Karl Rove wants the conservative faithful worried and motivated in November. Nothing motivates me more than the fear that John Kerry might be President.
Finally, the debates will be a major influence on the election. From what I have seen, Kerry has a hard time uttering a coherent sentence. He is has no real grasp of issues and relies solely on one sentence talking points (empty suit). He is lost and incoherent when he has to vary from his script.