But still, it's nowhere in the constitution beyond Right to peaceably assemble and the right to petition the government. The way I look at it, you would still have the two parties as a necessity. Otherwise no candidate gets 50% of the vote, and congress decides who becomes president. That is not going to change without a constitutional amendment. All the 3rd parties would be more like influencers to the main two. When looking at a primary, one might be a progressive party member/democrat or a green/democrat and who they chose to vote for could be influenced by the 3rd party endorsements. We don't have to have a parliamentary like party system as we do not have that organizational structure.