by Sazari » Sun Nov 18, 2012 8:40 pm
It's not parliamentary systems that drive the two party system, its the winner take all system that all but ensures we will have two and only two parties for as long as the current system is in place. Britain's system is actually similar to ours in this respect, in that it is very much a plural system. This is why you seem Labor/Tory for the most part dominating the system, because it is quite plural.
When the legislature is based on single member districts, it is going to naturally divide into two and only two parties. This is because there is zero advantages to claiming any proportion of the vote unless it is a plurality. This makes voting for anything outside of the two parties quite infeasable. We caquite easily see it in our system today, most people vote democrat or republican because even if you don't alight with the party, you won't vote for a third party because they stand no chance of winning, and they gain no representation unless they win.
Contrast this with proportional systems, where if a party takes 5% of the vote, they get 5% of the seats in the legislature. You can easily vote for a 3rd, 4th or 5th party because even if you only capture a small amount of the vote, you still capture a small amount of the legislature. In america, if you capture 5% of the vote in every congressional district, you will end up with 0% of the congress.
This is why everyone who talks about 3rd parties seriously in an America system is just ignorant of basic political facts. We will never have a viable 3rd party because our system is way to plural to ever allow it.