Fusion voting is an extension of FPTP that relies on parties. Parties are not essential to FPTP, but they inevitably creep in, and fusion takes advantage of this. In classical FPTP at a general election, each party nominates a candidate, and the winner is he with the most votes.
Fusion voting allows two parties to share the same candidate. So if the Green Party decides that they are splitting votes off of the Democrats (and enabling Republicans to win), they ordinarily have one alternative: Don’t run.
With Fusion voting, they can nominate the Democratic candidate as their own. Now voters can “send a message” and vote for Gore on the Green ticket. If Gore gets 60% of the votes and half of them are Green-based, he can see that environmental issues are very important to a third of the country.
Advantages: “Sending a message”, as above.
Disadvantages: From my perspective, fusion doesn’t really have any disadvantages, but lots of folk question whether it will do any good in MA. Democratic legislators are rarely in any danger of losing their jobs to Republicans, so even if you send them a message, they probably won’t listen because they know they’ll get re-elected anyway. Competition comes in the primaries, where fusion voting (being based on parties) doesn’t help. There’s two state-wide jobs that Republicans can win (Gov and LG) and certainly fusion voting will help these races… but pretty much no others.
IRV stands for “Instant Run-off Voting” and is a form of “preferential voting”. Preferential voting means that instead of voting for one candidate, you rank the candidates and your second-place, third-place or even fourth-place preference actually matters.
In IRV specifically, if no candidate gets 50%+1 of the votes, then the candidate with the fewest first-place votes is eliminated from all ballots. (So if your prefence was A > B > C, and B is eliminated, your ballot is now treated as if it said A > C.) Lather, rinse, repeat. Eventually, a candidate will be selected.
Advantages: Vote-splitting and the tactical “vote for the lesser of two evils” are eliminated. You can put the Green as your first choice, the Democrat in second, and if/when the Green is eliminated, your vote will count for the Dems.
Disadvantages: As with all preferential voting systems, the ballot can get very large. Also, it’s possible (but not very likely) for a candidate to be second place for everybody and first place nowhere, and thus lose straight off even if he’s the one everybody likes (but not loves). Tactical votng still exists, but the effect is lessened.
Condorcet: Another preferential voting system, the ballot would look exactly the same as in IRV. Rank the candidates, and cast your ballot. Behind the scenes, candidates are compared pair-wise. Almost always there will be a candidate, A, who wins (head-to-head mano-a-mano) against any other single candidate.
Almost always? Yes, almost always. It’s possible to have three (or more) candidates where A beats B, B beats C, C beats A, and then there are a number of different mechanisms for breaking this three-way tie (or “Condorcet cycle”). For example, you might choose A because A’s margin over B is greater than B’s over C or C’s over A. Or you might run an IRV considering only A, B and C. Or…
Advantages: Avoids IRV’s possibility of dropping the candidate everybody likes (but nobody loves). Has all of IRVs other advantages.
Disadvantages: It’s complicated to explain; people may not “get it”. Tie-breaking may seem arbitrary. Fortunately, Condorcet cycles pretty much don’t happen… but if they do, the wrangling over the 2000 election might seem like child’s play. Cannot be extended for multiple-seat races (see below). A different forms of tactical voting known as “burying” can be used here.
Single transferrable vote: Another preferential system which can be thought of as an extension of IRV: You can elect more than one candidate at a time. Cambridge city council elections are run using this method. Nine councillors, all of them elected at-large (no districts), city-wide.
Instead of 50%+1, the goal is to get (1/(N+1))+1 votes. With nine councillors, you have to get 10%+1 of the votes. When a candidate is successfully elected, they are dropped from the ballots just like an eliminated candidate, except… well, if the criteria is to get 1000 votes and you get 1500, it hardly seems fair that 500 votes are “wasted”. So under STV, they are not vasted.
Two common ways of handling this: All 1500 ballots that elected candidate A are treated as 1/3 of a ballot going forward. After all, you can’t say which thousand ballots of the 1500 elected the candidate… OR, you can do as Cambridge does and randomly pick 500 ballots out of the 1500, and throw them back in the bin while the thousand that elected the candidate are removed from the process.
You can see the entire process here.
Advantages: Well, if you’re like me, you might sometimes question the validity of geographical-based candidates (especially when the district is heavily gerrymandered). I have a lot more in common with a liberal computer programmer in Springfield than I do with my next-door neighbor here in Natick. STV allows multiple districts to “merge” and jointly elect the candidates.
Disadvantages: Very complicated. Very, very, very complicated. Has all the disadvantages of IRV, plus is a bit harder to “get”.
That’s about it for this quick summary. There are many other voting systems out there, but none that are in use in this state or being proposed for the state.
For more information on systems I’ve mentioned and systems I haven’t, I highly recommend Prof. Douglas Amy’s “Proportional Representation Library“.
A quick note on tactical voting: all systems are vulnerable to some form of it. The question becomes how obvious is it, and how willingly will people do it. Arguably, the method is pretty obvious under FPTP and it’s quite common. One question to consider is whether any other system will make it rarer…