It the RCP national average that concerns me. I doubt Kerry or Gore were up much, if at all, for a sustained period in October in the RCP average.
It was actually Bush who led for most of October 2000, and then his numbers dropped hard in the final days (likely due to the DUI), proving anything can happen.
Ask yourself how RCP could possibly average all the polls, since they all have different compositions, timings, etc, etc.
Answer: the polls cannot be averaged together. There is no possible succesful weighting scheme.