Here are a few more of the factors that "cost" Gore "his" election:
1) Of those Americans who bothered to vote, nearly half voted for Bush.
2) Gore ran an inept campaign, shunning Clinton's stained coat-tails and walking away from Ohio and other key states.
3) The outcome of the election was decided by a political coup to which our corrupt electoral system assented, rather than suffer too close an examination into its processes (which, like sausage-making, are best not observed by the weak at heart).
4) The American public complacently accepts a system which increasingly serves the interests of the wealthiest citizens and corporations.
5) The Two Party System prevented Nader from participating in the electoral process. Possibly if his views received a fair hearing, he might have, oh I don't know, WON?
In the baseball of politics, the Two-Party System has bought the stadium, the broadcast rights, the teams, and the sponsors. Anyone who doesn't want to play baseball will be locked out. Like Nader, they will be scapegoated and vilified by those protecting their interests.
Voting patterns show that the electorate is looking for something aside from this game, but the one-party state called the Two-Party System won't let anything else on the air.
Nader only "spoiled" the election if you believe that the presidency belongs to the Two Party System. If you happen to believe in the quaint notion that the presidency belongs to the citizenry, then it was Nader whose candidacy was "spoiled."