This is the idea that a voting system can have a majority faction force the victory of one of its candidates over the minority. The issue I have with discussions on this is that there is practically never a majority of folks united on every issue - you have two sides who, in a “compromise” of sorts, have to take extreme stances on several issues to get votes. Polarization has nothing to do with the voters, and everything to do with their attempts to get the little utility possible by picking one extreme over the other. If we made it possible for a candidate with extreme stances on some issues and moderate stances on others to run and win, there would assuredly never be a majority for or against ever again, but just all the voters trying to fight it out over individual issues. This kills gerrymandering, as even districts where a majority of people agree on an issue may have the minority take over instead, in a “trade” of sorts, and vice versa.
In proportional systems, you still have majority-forced victory. It’s just a different type of majority forced victory where the majority instead force the election result to one in which they win >=50% (> if odd number of seats) of the seats, and thus (if they are unified) 100% control over what legislation is passed. The only way for a voting method, (whether it be proportional or majoritarian/utilitarian) to not give the majority the ability to force a victory is to sacrifice essential voting properties such as clone-proof (like in anti-plurality voting where voters vote against their least favorite candidate and the winner can be decided by which side runs the most candidates that the other side has to split their votes between) or even worse, non-dictatorship. Tyranny of the majority will be a problem in all voting methods, but less so in some then others because some voting methods (aka FPTP) do a lot more then just give a majority of voters the ability to force a victory: they encourage voters to form into unified polarized teams and thus make it much more likely that a majority of voters will unify against the minority.
In a proportional system, how likely is it that there is a 100% united majority? The less united they are the exponentially more compromise and minority representation that happens. I thought the idea of PR is to so perfectly represent voters that majorities can form on each individual issue in the way the voters would form - if it doesn’t do this, it’s almost pointless, isn’t it?
The main tactic* involved in gerrymandering in the US is by minimizing the number of votes that your supporters waste (either because they merely pile on to the margin of victory, or because they are cast in a losing effort) and maximizing the number of votes your opponents waste. Even without a completely united majority, a group won’t need to make concessions to every single voter to win. The voters they don’t need are the wasted votes. If they get their support anyway, the votes are considered wasted for being superfluous, if they don’t get them, they are wasted for being cast in a losing effort. So long as there are wasted votes, that is, voters whose support is unnecessary to win the election, gerrymandering will still be possible.
*Another tactic would be increasing the ‘cost’ (i.e. number of votes needed to win) of your opponents’ seats, for example, through unequal district sizes, but this is illegal in the US when redistricting.
The maximum amount of gerrymandering would go down significantly, especially over a few election cycles, wouldn’t it? Voters would start contesting new issues, the minority part(ies) would have a way to get their message out in the issues where the majority is united, etc. Actually, I’d say most gerrymanderers would be terrified with a new voting system, since they have little data to go off of. Getting them to avoid alerting the major parties would be the real trouble, because otherwise these systems would be simultaneously attacked for not ending gerrymandering, while being opposed secretly because they limit gerrymandering. It’s quite a journey to any reform on this topic.