The government has pre-approved the Democratic and Republican factions of the one-party system. Taxpayer money funds their conventions, primaries, and presidential elections. Ballot access restrictions keep other "parties" off the ballot unless they jump through impossible hoops. It is the Bolsheviks and Mensheviks only Americanized. The campaign reform law has turned the two parties into a pre-approved "nobody else need apply" organization that forces all political dissent to associate with one or the other faction. Campaign reporting laws prevent anyone from donating to anything but the approved parties out of fear of retribution by having to be on a list.
It goes on and on.