Good question. I know the national Green Party has not yet had it’s convention. What is the status of the Libertarian Party? The likely winner of the Green Party is Dr. Jill Stein who ran for governor against Mitt Romney a while ago.
Probably only major party candidates. Gary and Jill have about as much chance of winning the presidency as Pat Paulsen did.
If Bernie were to have an 11th hour change of heart and decide to head to the Green Convention to get their nomination, he would more than likely beat Stein for the nomination and make her his running mate. The Greens more or less reached out to him and guaranteed him the nomination should he seek it. The Greens are also on the ballot in all 50 states, so he would be on all state ballots in November.
He could end up getting 20 percent plus in the polls immediately, similar to Perot's numbers and make this a three way race, but instead of Perot's presence in the race clinching victory for Bill Clinton in 1992, Sander's presence as a 3rd party candidate would likely clinch it for Trump with Sander and Hillary Clinton splitting the liberal vote.
Sanders would definitely qualify to be on the debate stage with Trump and Clinton due to greater than 15 percent support in the average of polls. Maybe he would also get national security briefings, since he has a large percentage of the vote and there being a slim chance he could win it if he could pull even with Clinton and Trump.