Thanks to Daily Kos for pointing out the terrific piece by Mark Mellman, who discusses the very little known fact that Kerry's polling numbers are better at this point in the race than any other presidential challenger since the inception of polling numbers. A key section,

I keep referring to “this point in time.” Why? Because campaigns are events that unfold over the course of the cycle. Most of the movement in polls comes in the aftermath of the conventions. Incumbent presidents are the best-known politicians around. Challengers are usually not as well known. Kerry is no exception. Today, many voters are expressing a preference for the Kerry they don’t know over the Bush they do. That is striking. Often, unpopular politicians still lead at this stage.
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With just 44 percent support in both of the two most recent polls, Bush is in real and serious trouble.