[G]et states to adopt “alternative voting.” One reason independent, third-party, centrist candidates can’t get elected is because if, in a three-person race, a Democrat votes for an independent, and the independent loses, the Democrat fears his vote will have actually helped the Republican win, or vice versa. Alternative voting allows you to rank the independent candidate your No. 1 choice, and the Democrat or Republican No. 2. Therefore, if the independent does not win, your vote is immediately transferred to your second choice, say, the Democrat. Therefore, you have no fear that in voting for an independent you might help elect your real nightmare — the Republican. Nothing has held back the growth of independent, centrist candidates more, said Diamond, “than the fear that if you vote for one of them you will be wasting your vote. Alternative voting, which Australia has, can overcome that.”
I don't think instant runoff voting would radically move our system, but I think it would be a big improvement. It might be used to elect some “centrists,” but I really think that would be a minor effect. The bigger gain would be allowing accountability in solid red and blue districts and states. Places where people might want to unseat a governor or senator because they seem corrupt, but the voters don't want to move ideologically in the other direction. It would also allow third parties to gain traction. Not so much to gain a huge number of seats, but to inject new ideas into the system. Traditionally in this country, third parties have also been a source of new policies. While these third parties fade away, it is often because a major party co-opted most of their platform. The third party starts losing elections, but after winning the the war on policy.
I know some people, like Matthew Yglesias, support proportional representation. Proportional representation is where multiple members are elected from a single, larger district, and the winners are selected based on the relative share of the vote each member or party gets. While I think it is a good idea in the abstract, the problem is that it is pretty meaningless in this country without massive changes through constitutional amendments. Therefore, it is misguided to make it part of a push for election reform.
You simply can't do proportional representation for president, governor, or senator and you can't do it properly for House races in over a dozen states. These are the positions that dominate our politics. The number of national office races that could be affected by proportional representation would be relatively small.
Making the electing of House members “better” only for the big states is basically worthless because the Senate is still the choke point. Proportional representation might, in theory, help elect third parties from some big states get to the House, but it will not help third parties gain traction in runs for the governorships or the Senate. Without being able to field candidates in those races, I don't see how third parties would not end up in the same shape they are now.
Proportional representation might be good in theory, but due to the constitutional limitations of our system, it's effect in this country would be very small. Instant runoff voting, even if you think it is a less perfect system, would have a much greater reach, so probably could do dramatically more good. It is one of the only positive changes to how we elect all our politicians that, I think, is achievable without massive constitutional changes.