I don’t honestly know. Both of the primary parties are going to fight it tooth and nail because it would weaken them drastically and the last thing they want is more competition for votes. I think the only thing we can realistically do is keep spreading the message until the majority of the population is behind the idea just like the ground swell that’s working to get marijuana legalized. The problem of course, is that it’s not really an exciting thing to get people behind, it’s a pretty dry technical issue. So in the meantime, I guess just keep educating people, and keep putting pressure on elected officials to push for it.

Edit: Thinking about it more depending on how things go with the GOP there might be an opportunity there. If E.G. Trump or one of the other extremists manages to fracture the GOP into two competing conservative factions that neither have enough votes to win with we might be able to get conservative voters and politicians to actually back proportional voting as a pure survival tactic. At that point we’d only need to get a small subset of progressive politicians/voters to support it as well.