When it comes to US, adding more candidates doesn't change the politics. Genuine grassroots campaigns have an almost impossible climb against establishment endorsed candidates in both major parties, and creating your own party does nothing either. Without a large battle chest, you ain't gonna win against a candidate with a huge corporate campaign budget. If anything, adding more candidates creates a "spoiler" effect, where the establishment candidate doesn't need as many votes, because the opposition vote is split due to two or more opposition candidates. And even if you manage somehow to get elected, you'll have a hard time getting anything done if you don't tow the party line.

The US system steers naturally towards two parties that both advance corporate interests, and that's what's happening now.