Altruists and envious people who meet in contests are symbionts. They do better than a population of narrowly rational individuals. If there are only altruists and envious individuals, a particular mixture of altruists and envious individuals is evolutionarily stable.

It can be advantageous for an office motivated party A to spend effort to make it public that a group of voters will lose from party A's policy proposal. Such effort is called inverse campaigning. The inverse campaigning equilibria are described for the case where the two parties can...