I am a reductionist. I have a hammer, and everything looks like a nail. Actually, I have a few hammers, so I subdivide the nails. But they are, in the end, all nails.
One of my favorite hammers is what game-theory types call "coordination," a hammer created to pound a nail called the tragedy of the commons. A tragedy of the commons happens when everybody does what's in their best interest, and the result blows up in their face. The classic example is the fishery. If all of the fishermen in a particular area agree not to overfish the fishing ground, there will always be enough fish to catch. But if someone cheats, the cheater gets more fish than anyone else, and, more important, if he is the only cheater, the fishing ground continues to thrive and no one notices. Thus, it is in each fisherman's interest to cheat. But if they all cheat, the fishing ground is destroyed, and they all lose. This is a tragedy of the commons, and it is prevented by the establishment of enforceable rules against cheating.
But I'm not here about fishing. I want to talk about gerrymandering, the practice of drawing Congressional districts to make them most favorable to the party in power in the state legislature (which draws the districts). The "commons" here is the US House of Representatives (our version of the UK's House of Commons!), to which we send representatives to advance our political interests. As partisans with political interests, we each want our party to have as many House seats as possible. But as citizens, we want the House to be a functioning legislative house, not a dysfunctional mess. The only way to assure a House the works is to send Representatives who represent their entire districts and are able, therefore, to compromise on issues that have the support of the majority of the people in their districts. But the best way to get the most members of your party in the House is to gerrymander - to "cheat" on the policy of full representation in order to get an advantage for your party.
The method is very simple, when the Congressional districts are redrawn periodically, the majority party in the state legislature figures out a way to make as many districts as possible "safe" for that party's members. That usually means drawing districts that consist, to the extent possible, of (i) 100% minority party voters, or (ii) a significant majority of majority party voters.
Suppose there are 140 Democrats and 160 Republicans in a state, and the Republicans control the legislature, which has to create three Congressional districts of 100 voters each. If the population is divided equally, the Republicans will have a registration advantage in every district, but not a "safe" seat, as an immoderate Republican might well lose to a moderate Democrat in any or all of the districts. If, instead, the legislature can put 100 Democrats in District 1 and split the remaining Democrats evenly between the other two districts, then two of the districts will be safely Republican, consisting of 80 Rs and 20 Ds each. The ration of R's to D's is 8 to 7, but the ratio of R Reps to D Reps is 2 to 1. Nothing to it.
If the majority party assumes that anyone who can command the votes of half its primary voters is a good choice for Congress, then it is always in that party's interest to create these gerrymandered districts. Unfortunately, that assumption is not correct. By making a district safe for either party, the state legislature effectively makes that party's primary the key election in each Congressional cycle. Thus, the majority party within each district elects the Representative from that district. Or, to put it another way, to become the Representative from a district, a candidate need appeal only to a majority of the primary voters of the majority party in that district.
History has begun to show us that the most liberal Democrats and most conservative Republicans tend to win these safe district primaries. Why? Because "electability" is not an issue there. If more than half of primary voters are either very liberal or very conservative, but the winner of each primary would have to get a substantial number of votes from the other party to prevail in the general election - because, say, a substantial part of each party would prefer a moderate from the other party to an ideologue of their own party - the primary voters will have to take into account the electability of its party's primary candidates. Thus, even if the majority of the voters are ideologically far from center, they may vote for a moderate of their party over someone who shares their ideological views to assure that their party wins the seat in the general election. Without this electability consideration, however, the ideologically inclined voters have no incentive to vote for a moderate candidate, and both parties end up putting an ideologue in the general election and, by virtue of the party's overwhelming majority in the district, in the House.
Gerrymandering destroys the commons of the House in two ways. First, by assuring itself that it will dominate the state's Congressional delegation, the party establishment of the majority party loses control of its Congressional delegation, because ideologues win the primaries over the establishment's candidates. At least, that's how it works until the ideologues become the party's establishment. The result is that the people who go to Congress do not know how to be legislators and, even worse, don't even know how to be party members. Party caucuses are refractory precisely because the parties have finagled the state process to get the largest possible caucus.
Second, by sending ideologues to Congress, the party loses the ability to get anything done in Congress, because the ideologues from both sides refuse to do anything together. Thus, even the ideologues who get elected fail to accomplish their agenda, unless their agenda is to stop Congress from acting at all, which for some of these people is the case. But that is not their party's agenda; it is their agenda. And, thanks to their party's stupidity, the obstructionist agenda is the only agenda that is served.
The pernicious effect of gerrymandering can be seen in the so-called "Hastert Rule," whereby Republican Speakers refuse to bring to the floor of the House any bill that does not have the support of a majority of Republicans. (The Democrats don't follow this rule when they are in the majority, which probably means that they aren't gerrymandering as effectively as they could.)
Under the Hastert Rule, electability is replaced by passability, and the same game that occurs in the elections is repeated with respect to legislation.. A bill that a majority of Congress would approve can effectively be vetoed by a majority of the majority, which might be as few as 26% of the House's members. One might ask why a more statesmanly Speaker would permit this sort of rule to apply. The answer is simple: the Speaker is elected by his or her party. In the case of the Republicans, so many ideologues have been sent to Congress thanks to gerrymandering that the Speaker who does not enforce the Hastert Rule will lose the job of Speaker. A majority of the majority insists that the Speaker impose the rule. And that is so because a majority of the majority are ideologues with no clue at all how to be legislators.
Gerrymandering thus cuts to the very heart of the small-r republican form of government the founders intended. Gerrymandering does not just disenfranchise individuals by making their vote in the general election nugatory. Gerrymandering degrades the quality of the people who win general elections by relieving them of the need to represent their district as a whole, by making it unnecessary that they have the expertise in the statecraft that makes a republic better than a mob. Gerrymandering sends to Congress Representatives who do not represent - legislators who do not legislate - politicians not only unversed in the art of the possible, but wholly uninterested in acquiring it.
Old as gerrymandering is, Congress was not always affected by it.