October 5th average post debate poll on the front page of www.pollingreport.com
Likely voter polls if available, multicandidate polls if available.
Bush 47 5/8 % Kerry 45 7/8 % so Bush on average ahead by 1.75%
Nader is averaging 1 4/7 % in polls including him.

Make Nader 1 5/8 % so undecideds average 4 7/8 %
so one would consider the race tied if one expected Bush to get 25/71 of undecided voters.

That is one would consider Kerry marginally (and not of course statistically significantly ahead) if one assumes one third of undecided voters end up voting for the incumbant.