It doesn't assume anything. It registers evidence for one hypothesis over another. If the evidence doesn't move your priors at all, then you're not thinking rationally. Of course there are other factors as well (which perhaps dominate), the strictness of the Dem/Rep split, etc. but this one piece of evidence should move you in the direction described.
That isn’t evidence for anyone voting based on race or that Oregon having more whites voting for a black person makes them less racist. Just being a different color has absolutely nothing to do with any of their qualifications, policies, personality, opponent, and more. Assuming race is the biggest factor based on the voters race and the candidates race is extremely racist in itself. An outcome alone based on race doesn’t determine the motive of voters. Even just candidates campaigning in a specific area would result in very different numbers.
