DNC04: Negative Bounce?

A USA Today poll suggests that President Bush picked up two points against rival John Kerry post-DNC. Given that the margin of error for the poll is +/- three points -- the true "difference" is that the results of that poll aren't statistically significant, regardless of what a pundit says. A Washington Post poll, on the other hand, shows Kerry with a six point lead over Bush (50 percent to 44 percent); also with +/- three point variance. Why the (seeming) difference in results? Who was asked and what was asked. The election remains too close to call. See Boston Globe, USA Today, Washington Post