What State will be the first to vote for a 3rd party candidate? When will it happen?
In what election? Currently, Vermont elects a socialist Congressman. Vermont might also elected a "Progressive" Governor this year who is a protege of Bernie Sanders...although he is running as a Democrat just for this election.
Connecticut, Maine, Alaska, and Minnesota have all had 3rd party or Independent Governors in the recent past. But all of these were much more "cults of personality" than legitimate 3rd party movements.
And for the libertarians, if you guys want to be taken seriously, stop running candidates in every election that fail to get 1% of the vote. You're just embarrassing yourselves when you keep whining about not being respected as a major party, but never backing it up at the polls. If you're really serious, move to New Hampshire and restart your crusade at the local level.
For any third party to ever make a dent, they will have to win some local elections, and then, state-by-state, convince state legislators to change the vote counting rules to something like preferential voting. The Libertarians, Greens, etc, will never get anywhere with first-past-the-post.