The weeks after Kerry picked Edwards but before the Dem's convention, after the first debate, and about 5 days before the election before Kerry wasted time on states like Nevada and Flordia instead of focusing on Ohio.
That's because at the time, Ohio wasn't being looked at as a big swing state. After 2000, the Dems were hell bent on winning Florida. They spent so much time and money there with no result at all. Truly a large mistake on their part.
Granted they might have been able to pull it off if they had spent as much time campaigning as they did trying to throw Nader off the ballot.