http://en.wikipedia.org/wiki/Proportional_representationThat's the only way to have a viable third, let alone fourth, fifth etc. party.
And that, in turn, is the only way to keep wingnuts on both sides from getting more influence than they're supposed to have.
The good news is, it's super effective: You have First-past-the-post representation as an inheritance from British rule, New Zealand used to have it too, for the same reason. In 1994, NZ passed a new law to go to mixed-member proportional representation instead.
http://en.wikipedia.org/wiki/Mixed-member_proportional_representationAnd already from the next election, in 1996, the two-party system was bust - no party has been able to rule without a coalition since.
Some states have popular demand referendums as an option, right? You could get the ball rolling today, if'n you really want it.