Imagining the Danger of 2000 Redux
Presidential race is close enough in number of key states that human error, technical foul-ups and legal challenges could delay results for days or weeks, in unwelcome replay of 2000 election; questions about legitimacy of Bush presidency and fairness of 2000 election have never died; scholars say that if either candidate wins without leading popular vote, as George W Bush did in 2000, there could be serious calls to abolish Electoral College; drawing; photos (M)