This is a consequence of the winnertakesall voting system . In a voting district in the US , only the party with the most votes gets anything , so there ' s no point in voting for a third party candidate . It ' s only worthwhile to vote for a party that has a good chance of winning with 50 % of the votes . If you want to vote against the Democrats your only option is Republicans , or vice versa . Compare that to e . g . Germany , where a party that gets 30 % of the national votes gets 30 % of the seats in the legislature . So even if you really hate the # 1 party you don ' t have to vote for the # 2 party you can vote for whoever you want , and even if that party isn ' t 50 % of the vote it will still make a difference .