One not infrequently hears the claim that a politician did something "for political gain", and the claim is said in a context that suggests that it follows that there was something sordid, ignoble or even wrong about it. But why accept such an inference? Suppose that politicians promote their political capital in order to enact policies that they think are good for the country. If so, then the claim that a politician did something for political gain need not be a criticism: one might as well say that the politician did it for what he or she thought was the good of the country.
It may, of course, be that people who use that phrase are cynical: they do not believe that politicians are trying to promote the good of the country. But I doubt that such a cynical thought can be very often justified. Even if a politician is misguided, stupid, greedy or power-hungry (and most of us exhibit these traits at times), it can still be the case that the politician is nonetheless trying to promote the good of the country. Such a hypothesis is both charitable and consistent with what we know about human nature.