One workaround would be to assign high confidence only to beliefs for which you have read n academic papers on the subject. For example, only assign 90% confidence if you've read ten academic papers.
If you have read 10 papers on a political question, all the papers are concurring, and they represent the entire body of literature on that question, then 90% can be warranted. I strongly suspect that if you do a fair review of any question there will be a tremendous amount of disagreement, however, and a well-calibrated observer would rarely approach 90% without strong pre-existing ideological biases subverting their estimation processes.
I have read quite a few macroeconomics papers, and there are very few non-trival things that I would assign a 90% probability to, and almost by definition those aren't the sort of things people talk about in "political discussions." The more you read the more humble you become with respect to our level of knowledge in the social sciences, especially if you are literate in the hard sciences. If you expect your knowledge to cash out in terms of predictions about the world, we don't know much. This is why if you ask an economics professor almost any question of substance, they will provide you with a lengthy docket of caveats.
I agree with all of this.
So you're playing the credence game, and you’re getting a pretty good sense of which level of confidence to assign to your beliefs. Later, when you’re discussing politics, you wonder how you can calibrate your political beliefs as well (beliefs of the form "policy X will result in outcome Y"). Here there's no easy way to assess whether a belief is true or false, in contrast to the trivia questions in the credence game. Moreover, it’s very easy to become mindkilled by politics. What do you do?
In the credence game, you get direct feedback that allows you to learn about your internal proxies for credence, i.e., emotional and heuristic cues about how much to trust yourself. With political beliefs, however, there is no such feedback. One workaround would be to assign high confidence only to beliefs for which you have read n academic papers on the subject. For example, only assign 90% confidence if you've read ten academic papers.
To account for mindkilling, use a second criterion: assign high confidence only to beliefs for which you are ideologically Turing-capable (i.e., able to pass an ideological Turing test). As a proxy for an actual ideological Turing test, you should be able to accurately restate your opponent’s position, or be able to state the strongest counterargument to your position.
In sum, to calibrate your political beliefs, only assign high confidence to beliefs which satisfy extremely demanding epistemic standards.