In 1993, New Zealand switched from the traditional British first-past-the-post, single-member-district system of electing members to Parliament, to a German-style mixed-member system, in which some members are elected from single-member districts and others are elected from a national “party list”.
I have long been a member of the Center for Voting and Democracy (www.fairvote.org), an organization dedicated to introducing pro-multipartisan electoral reforms, such as proportional representation and instant-runoff voting, in the United States.
I have a pet theory: The first-past-the-post system, by freezing out all but the two biggest parties, naturally produces a system in which the parties are big coalitions of several different factions. Here in the U.S., the Republican Party includes pro-big-business interests; neoconservative foreign-policy warhawks; religious-social conservatives; nativist-isolationist populist conservatives (like Pat Buchanan, who is trying to siphon these off into his own new America First Party); moderate libertarians, like Goldwater was (radical libertarians join the Libertarian Party but some continue to vote Republican anyway for strategic reasons); and a core of more traditional, middle-class, moderate conservatives. Obviously these groups don’t see eye-to-eye on everything, but they all stay in the same party, because where else are they going to go? But if we were to switch to a PR system, so that a given faction would no longer have to work within a major-party “big tent” to get its own representation in Congress, then the Republican Party probably would break up, along its natural fault lines, into several medium-sized parties. And so would the Democratic Party.
At least, that’s my theory. It can be confirmed only by observing how things go in a democratic country that has had a first-past-the-post system for a long time and then switches to PR. But when I look around the world, I see only one such example: New Zealand. (There’s also South Africa, but the difference between the old Apartheid regime and the current system is too vast to control for just one factor like the introduction of PR.)
New Zealand Dopers, please enlighten me: After NZ switched to PR, what happened? Did any big parties break up? Did big parties lose ground to smaller ones? What practical political effects have resulted from the change?