"Committed" Democrats are driven by "hate Bush". And precious little else. In total, they amount to maybe a third of the country. Uncommitted Democrats and Independents don't hate Bush and, indeed, are a little put-off by the left's histrionics and hate-mongering.
The historically low turnouts in the Democrat primaries since Iowa and New Hampshire strongly suggest that Kerry's support is exceedingly thin. He's been hard-pressed to capture even a slight majority of a light turnout, remember. It was Dean that created excitement for the Democrats and brought new voters into the party. But, now, they have left the building.
In the end, Bush's GOP supporters will show up at the polls. The middle will lean heavily toward Bush. And many of Kerry's Democrats will stay home, thoroughly disspirited by the candidate they perceived as "electable" -- only to discover he was anything but.
It could be a big win.