Until a political part emerges that isn't cram packed full of ideological purists and crazies emerges, they will not be taken seriously. Cynthia McKinney? I rest my case. The last great third party was the socialists of the 30s. Those days are dead and gone and so are third party politics for the time being.
There aren't any ideological purists and precious few 'crazies' in the Democratic Party. That's the whole point of the party - it has no ideology, its just the wishy-washy centerish alternative to the crazy right-wing party.