My brother voted for Nader (his vote did not give New York to Bush) but I told him that a vote for Nader was essentially a vote for Bush, but you see, that was an indicator of Gores weakness as a candidate (theres no way my brother would have ever voted for either Bush and yet he voted for Nader, and blamed the Supreme Court for electing Bush.)
These are the simple facts. 50 States voted, Gore did not carry enough of them. One of the states he lost, by a very narrow margin was Florida. We can point to several different factors which may have contributed to his loss nationwide (like him "running away from Clinton.) Personally, I think his advisers should have Let Gore be Gore. (After the election, when he spoke out against the actions of the Bush administration, he showed more fire in the belly than he ever had during the campaign.)
Eight years earlier, Bill Clinton also lost in Florida, and yet, still beat the incumbent President (who, in my estimation was a stronger candidate than his son.) That year, Ross Perot was a much more successful candidate than Nader was in 2000, taking almost 20% of the vote.
https://en.wikipedia.org/wiki/Ross_Perot_1992_presidential_campaign#Analysis
A 1999 study in the American Journal of Political Science estimated that Perot's candidacy hurt the Clinton campaign, reducing "Clinton's margin of victory over Bush by seven percentage points." In 2016, FiveThirtyEight described the speculation that Perot was a spoiler as "unlikely".