Despite their small numbers, Nader’s and Buchanan’s supporters provided the margin of victory for Bush. If Nader had not been on the ballot, Gore would have carried Florida and all of the other close states easily, giving him a comfortable electoral total of at least 292. [4] If Buchanan had not been a candidate, the Florida ballot might have been simpler to understand, giving Gore enough votes to win the national election simply by carrying the Sunshine State. Even without Florida, we might speculate–but cannot demonstrate–that an election without Nader would have enabled Gore to campaign in other winnable states (most obviously Tennessee and New Hampshire) and overcome his shortfall of only three electoral votes. https://www.uvm.edu/~dguber/POLS125/articles/pomper.htm

Also, Nader himself indicates in post-election analysis, quoting exit polls showing that 25% of his voters would have voted for Bush instead, but 38% would have voted for Gore (the rest would have voted for some else, or nobody). Nader got 10,576 votes in Florida; Gore lost Florida by 537 votes. Without Nader, Gore would have won Florida by 837 votes: 64% more votes than he lost by.

Without Nader, Gore would have won the 2000 election.