Belief propagation fail on my part. I had already read that Yvain post when watching that Haidt talk, but I still interpreted the behaviour he described in terms of ape social dynamics, forgetting that the average politician is probably more cold-blooded (i.e. more resembling the idealized agents of game theory) than the average ape is.

OTOH, the problems Haidt describes (global warming, rising public debt, rising income inequality, rising prevalence of out-of-wedlock births) don't have a hard deadline, they just gradually get worse and worse over the decades; so the dynamics of brinkmanship is probably not quite the same.