The millions who voted Republican were likely always going to vote Republican anyway, regardless of the candidates. So they aren't a useful part of the equation.
The millions who didn't vote were likely not going to vote anyway, regardless of the candidates. So they aren't a useful part of the equation.
Without a Nader on the ticket it is probable that those votes would have gone to Gore (or to no one at all), as the average Nader supporter is unlikely to be able to stomach voting for a Republican.
In view of the closeness of the election I think it is perfectly reasonable to say that he lost the election for Gore.
There was never a snowball's chance in hell he was going to win.
Lost votes. Lost Gore votes