The two party system is an inevitable outcome of the election system we have. The game theory dictates it. Switch to approval voting(http://www.electology.org/approval-voting) and we'll have a much more responsive and ethical government.

In a winner take all system, if there are more than two candidates, the dominant effect is the spoiler effect, where having more similar candidates makes it less likely that any will win. This means that anything more than two parties is degenerate, which implies that only the dominant eigenvector of political opinion will ever be reflected in an election. (Which in the US is typically the culture wars/identity politics, unless the economy is falling apart.)