Sheehan and Nader gave up on the Democratic leadership because of it's inability towards reform (or rather it's unwillingness - hell, remember how hard Sheehan campaigned for the Dems as long ago as last year),
She never campaigned for the Dems. Last year she was writing articles bashing the Democrats for lewrockwell.com
not because they particularly hated the idea of the party in the first place.
Oh really? Then why does Sheehan bash the Democrats calling us the party of slavery and creating the Federal Reserve (usually an extreme libertarian rant) and a bunch of other crap that basically says the Democratic Party is the most evil institution in the country's history? That goes a lot more than just being annoyed with lack of reform.
Plus the idea that both Al Gore and GWB were pretty identical wasn't too difficult to believe back in 2000, don't you remember at all how uninspiring and how avoiding-of-issues both candidates were - Plus here I should make much of the fact that Al Gore has shares in Occidental petroleum (.. Yes, yes I know Nader has shares in Halliburton, thank you.)
No, anyone with half a brain could see policy differences.
The difference between Gore and Nader is I don't expect Gore (or any other candidate) to be perfect. This reminds me of a great quote from openly gay and ultra-progressive Rep. Barney Frank. When asked how he could support Kerry even though Kerry didn't support gay marriage he replied "I've only voted for a perfect candidate once in my life. Once I ran for re-election, I wasn't perfect anymore."
Nader on the other hand, bashes the Democrats for the slightest imperfection and expects us to worship at his feet when he is just as flawed. And Al Gore has never openly sided with James Dobson.
But regardless of what 2000 seemed like, that doesn't matter anymore as far as Nader is concerned, as in 2004 he clearly continued to spout the crap that Bush was exactly the same as Gore or Kerry and there was absolutely no difference between the candidates on issues whatsoever.
Or Do you consider Eugene Debs a Republican as he split the (mostly) Democratic vote?
Not really (his support probably mostly came from progressive Republicans) and the parties were way difference back then.
(One thing of note about the McGovern candidacy, despite the common myth McGovern actually did very well among blue-collar workers in the Democratic primary - especially in areas without very strong unions who were deeply embedded in the Democratic party structure, which mostly stayed with Humphrey. Once McGovern was nominated that supported faded away due to ambigous attitude of the party leadership. Without a doubt, McGovern would have won Rhode Island, South Dakota, Minnesota and quite possibly alot more states if it weren't for the attitude of the Party leadership)
And he still would've lost. McGovern is my favorite candidate of the 20th century, but he was also over 30 years ago and that election is barely relevant today.