It wasn't just the sit it out crowd. Not all the states were in compliance with the provisions of Section 303(a) of HAVA. There was suppose to be a purge of colorful 'voters' by January 1, 2006. So many of these voting pets, dead people, non existant addresses, duel residencies, et al stayed on the books and voted in November's election.
http://www.fec.gov/hava/timeline.htm