Unlike many, I don't blame Nader for the 2000 election. I, in fact, blame Vice President Al Gore, who ran an incredibly bad campaign -- one sufficiently dreadful that it actually transformed Governor George W. Bush from a punchline to a viable presidential candidate, and that it left us with having to rely on Florida to decide an election, which is rather like relying on a kitten to keep your ball of twine from coming unraveled.
Gore was the vice president under an immensely popular (if scandal-slimed) two-term president running against a charisma-challenged state governor. The last time we ran that script was in 1988, and Vice President George H.W. Bush read it word for word, embracing the notion of continuing President Ronald Reagan's legacy, and beating the pants off Governor Michael Dukakis. Gore, however, tried to distance himself from President Bill Clinton, which was remarkably stupid; he actually bought into the Republican propaganda, forgetting that Clinton's approval ratings stayed steady despite the best efforts of Special Prosecutor Starr and the Republican-led Congress.
If Gore had done what his opponent's father had done twelve years prior, Nader's third-party run would not have been at all relevant.
Anyhow, all that aside, all Nader's announcement accomplishes is to further damage a legacy that should be focused on his consumer advocacy, not his doomed runs at the presidency.