Politicians might have been tricked by an initial baseless belief in the efficacy of campaign spending, with the most popular candidates also raising the most money and creating a spurious self-fulfilling correlation. However, selection over time would be expected to wear away at such mistaken beliefs.

Not if incumbency advantage exerts such a powerful effect that selection on this trait has relatively little influence. Honestly, I do think that money helps politicians get elected, but it seems worth pointing out that there are structural reasons to suspect politicians might be wrong about this, due to poor initial calibration on the subject and a (possibly accurate) perception that experimenting unsuccessfully would have too high a cost.

(Also, very cool article! I love LW content that focuses on important and scientifically grounded domain knowledge!)