In a repeated game, where the same people play the same game over and over, cooperation can more easily arise than in a one-shot version of the game, where such people play only once and then never interact again. This sort of cooperation gets easier the more that players care about the many future iterations of the game, compared to the current iteration.

When a group repeats the same game, but some iterations count much more than others, then defection from cooperation is most likely at a big “endgame” iteration. For example, spies who are moles in enemy organizations will usually hide and behave just as that organization wants and expects, waiting for a very big event so important that it can be worth spending their entire career investment to influence that event.

Many of our institutions function well because most participants set aside immediate selfish aims in order to conform to social norms, thereby gaining more support from the organization in the long term. But when one faces a single very important “endgame” event, one is then most tempted to deviate from the norms. And if many other participants also see that event as very important, then your knowing that they are tempted more to deviate tempts you more to deviate. So institutions can unravel when faced with very big events.

I’ve been disturbed by rising US political polarization over recent decades, with each election accompanied by more extreme rhetoric saying “absolutely everything is now at stake!” And I’ve been worried that important social institutions could erode when more people believe such claims. And now with Trump’s election, this sort of talk has gone off the charts. I’m hearing quite extreme things, even from quite powerful important people.

Many justify their extreme stance saying Trump has said things suggesting he is less than fully committed to existing institutions. So they must oppose him so strongly to save those institutions. But I’m also worried that such institutions are threatened by this never-compromise never-forget take-no-prisoners fight-fight-fight mood. If the other side decides that your side will no longer play by the usual institutional norms of fairness, they won’t feel inclined to play fair either. And this really all might go to hell.

So please everyone, dial it back a bit. Yes, if for you what Trump has already done is so bad that no compromise is tolerable, well then you are lost to me. But for the rest of you, I’m not saying to forgot, or to not watch carefully. But wait until Trump actually does something concrete that justifies loudly saying this time is clearly different and now everything is at sake. Yeah that may happen, but surely you want Trump folks to know that isn’t the only possible outcome. There need to be some things Trump folks could do to pursue some of their agendas that would be politics as usual. Politics where your side doesn’t run the presidency, and so you have to expect to lose on things where you would have won had Clinton become president. But still, politics where our existing institutions can continue to function without everyone expecting everyone else to defect from the usual norms because now everything is at stake.

Added 21Nov: Apparently before the election more people on Trump’s side were talked about presuming the election was rigged if their side lost. Without concrete evidence to support such accusations, that also seems a lamentable example of defecting from existing institutions because now everything is at stake. HT Carl Shulman.