There are a lot of ways to deal with the problem: Brad Templeton has a good list. As a preliminary, this is what I currently think about the general situation.
The Hugo selection process is best thought of as two separate elections. The first is the nomination election, in which voters use an entirely write-in process to select a slate of five nominees in each category by simple plurality. The second is the actual Hugo election, where voters select a winner from the five nominees in each category using an “Australian ballot” instant-runoff system
Let’s talk about what happened this year.
The way to think about the Sad Puppies and their slate is as a political party. Essentially, what we saw was the rise of a political party (technically, two parties with highly correlated slates) in an election that has never had parties before. Parties are powerful for two reasons. One, they focus voters’ preferences onto specific candidates, increasing the power of their votes. Both Dave McCarty and Django Wexler explained how this works:
Let’s consider a hypothetical election between Green and Purple voters. There are 800 Greens in the voting pool, and 200 Purples. The Greens mostly prefer Green works, of which there are, say, 10 in serious contention — we’ll call those G1, G2, etc. The Purples similarly prefer Purple works, P1, P2, etc.This is why political parties are so powerful, and why U.S. voters will generally vote either Democrat or Republican even if they prefer a third-party candidate.
The Greens have no organization. Each Green picks the five works out of the ten that he or she personally likes best. Assuming each work has its fans, this will lead to a vote distribution that is reasonably even — say 95 for G3, 93 for G5, 89 for G8, down to 56 for G1.
If the Purples voted similarly, they would get a similar distribution: 34 for P2, 30 for P10, and so on. In this case, the ballot would be all Green, since the fifth-most popular Green work is more popular than all the Purples.
Instead, Purple Leader says, “Hey, lets all vote for P1, P2, P3, P4, and P5.” The Purples all go along with this. So those five works receive 200 votes each, and the others zero. Now the final ballot will be entirely Purple! The minority, by being more organized, runs the table. The Purples don’t cheat; neither have they suddenly become a majority. They simply have a more effective strategy, considered solely in terms of getting Purple on the ballot.
The second reason political parties are powerful is that they provide a shorthand for marginal voters. I do this myself: “I have no idea who to vote for in this City Council election, but I normally prefer Democrats, so I’m going to vote for their candidates.” This makes it easier for me to vote, and therefore more likely for me to vote.
We saw both of these dynamics in the 2015 Hugo nomination election. People who normally didn’t pay attention were motivated to vote because they could vote the slate without any further thought, and the existence of the slate focused their votes to make them even more effective.
Normally, this is all good and why we generally like political parties. We don’t in this case because of a divergence between the purpose of the parties and the purpose of the Hugos. In a normal political election, the parties are strongly correlated with the issues of the election. So when we choose to vote for the Republican party, we are choosing a set of policies that a Labour government can be reasonably expected to follow. The Hugos are different. The election is supposed to choose works based on overall quality, but the parties are choosing works based on some moral/ethical/political philosophy. Elizabeth Bear touched on this. So what is normally a good thing — a political party — becomes a bad thing.
Of course, one way to fight a political party is with a rival political party. Many people expect rival slates to appear next year, and for the Hugos to forever be a battle of slates, which means that the Hugos will be a battle of ideologies rather than a referendum on the quality of fiction.
This is not a simple problem to fix. Strategic voting — modifying your vote based on what you know or believe about the votes of others — is a powerful strategy, and probably a dominant one. But there are voting systems that minimize the effects of slate voting.
But remember, no election system is perfect, and choosing one is an exercise in trading off among various problems. It’s may be easy to reconfigure an election system to reduce the effects of a current set of abuses, but it’s much harder to design an election system that is immune from future abuses. Any changes should be examined carefully before being implemented.