Interesting post, I think I agree, but even if we should lower our confidence about almost all future predictions there should be some things that are more likely to happen and some actions that are likely to improve the outcomes of those things.
I would be interested in reflection about what those things might be, one possible example that comes to mind is climate change (which you mention) and another one is economic growth.
I think this is a great idea, I hope someone is crazy enough to try.
The key point might be that the most important EA ideas are not partisan (all existential risks, improved quality of aid, caring for the long term future) and could be adopted by more than 90% of parties in the Western world.
A less radical version would be "EA's who care about politics but don't identify with any party should overcome that shyness and evaluate which parties are they at least slightly aligned with, and which ones present to them the greatest opportunity."
In Europe there are several powerful parties, even in government, that have a structural problem attracting young people.
Another one would be that EA's trying to lobby for a particular idea should seek interactions with all parties until key ideas become the default option for everybody.
Whatever you give a man know that you are just a tiny bit of his life. He is struggling with giants. Try to be the most helpful tiny bit you can, but manage expectations.