Us vs Them would suggests two parties, not one-dimensional politics. If people are forced into coalitions, then the variation inside the coalitions should be orthogonal to the direction between the coalitions. But it seems to me that most of it is along the axis separating the parties. Maybe that's an illusion because it is salient - who is a swing voter, who can negotiate with the other party, etc. Moreover, when I look at a European country, I see a bunch of parties strung out along a single axis. This seems less likely to be an illusion, though I have less experience with European politics. How is this driven by Us vs Them?
Slovakia has a small libertarian party. So does America. The Slovak party is larger, partly because small parties are viable in a proportional system, and maybe also for other reasons reflecting a difference between the populations. That doesn't necessarily mean that the correlations between political positions are different between the two countries.
Moreover, the topic of the post is factual beliefs. Even if the structure of the coalitions causes people's policy preferences, that is a weaker claim than that it causes their factual beliefs. Maybe free-market Americans join the Republican party and come to oppose gay marriage and drug legalization, whereas free-market Slovaks join a different party with different influence. But I rather doubt that positions on gay marriage are driven by factual beliefs. Drug legalization might be, but it is probably a minor belief, a higher-order correction, compared to the important beliefs that drive their free-market positions. What I said I don't believe is that different coalitions drive the correlations between factual beliefs.
I said that when I look at a European country, I see a bunch of parties strung out along a left-right axis. But, actually, I guess I don't see anything, I just hear people describing the parties that way. Say, a left party L, a center party, C, and a right party R, allowing LC and CR coalitions. But often, when I look closely, they do seem to have exotic platforms that shouldn't rule out the LR coalition. For example, people were shocked by the British Liberal Democrats forming a coalition with the Tories, because "everyone knew" that they were a...
Here is a new paper of mine (12 pages) on suspicious agreement between belief and values. The idea is that if your empirical beliefs systematically support your values, then that is evidence that you arrived at those beliefs through a biased belief-forming process. This is especially so if those beliefs concern propositions which aren’t probabilistically correlated with each other, I argue.
I have previously written several LW posts on these kinds of arguments (here and here; see also mine and ClearerThinking’s political bias test) but here the analysis is more thorough. See also Thrasymachus' recent post on the same theme.