It seems to me that the most important political acts I can perform do not involve siding with one of the existing parties, or even necessarily to vote at all, but to try to bear witness through word and action to this double vision of the earthly city: a long defeat followed by a longer joy.
We are too prone, I believe, to think that voting is the definitive political act. That would be true only if politics simply belongs to the government. There is a far vaster sphere of politics — the life of the polis — that belongs to everyday acts of ordinary people. In this maybe Gandalf is a pretty good guide: “Yet it is not our part to master all the tides of the world, but to do what is in us for the succour of those years wherein we are set, uprooting the evil in the fields that we know, so that those who live after may have clean earth to till. What weather they shall have is not ours to rule.”
Methinks there are worse people than Gandalf to consult when it comes to wisdom re. politics.