While I favor proportional voting, I don't expect it to solve the problem because the legislature still works on an all-or-nothing basis. A law either passes or it doesn't. Adding more parties just tweaks the alliances and horse-trading that have to be formed to reach the 50%+1 required for it to pass. Those alliances have to be durable for the quids-pro-quo to work. You can call those alliances parties or not, but they work in similar ways.

Any chance would tweak the existing sets of alliances, and that would a time confuse and quite the partisanship. But sooner or later somebody is going to realize that pledging fealty to each other is the best way to get their personal priorities achieved. Partisanship happens because it's effective, and encouraging more parties won't deter the fact that 50%+1 of the country can shut the remaining parts out entirely.

Partisanship in the US these days has little to do with agendas and more about identity. Elections have become more about shutting the others out of power. I see that the article hopes that by introducing more parties, they can remove the urge to see one other party as the enemy to be destroyed at all costs.

But I don't think it works. A variety of social and political factors have pushed us here, and they won't be removed by rearranging the names of the alliances. The causes run much deeper, and tweaks to the process won't do more than confuse that for a while. So I'm all for proportional voting, or really any change, just to give me a break from the constant drumbeat of animosity. But I don't expect that break to last more than a few cycles, at most.