One of the conclusions of an AAPOR paper on the 2016 US polls contains this detail:
As this report documents, the national polls in 2016 were quite accurate, while polls in key battleground states showed some large, problematic errors. It is a persistent frustration within polling and the larger survey research community that the profession is judged based on how these often under-budgeted state polls perform relative to the election outcome.
The paper does support a lot of its conclusion with statistics, but there's no actual data about (poll) funding in it. So, is there some other data (in the form of say funding comparisons [which would have to take electorate sizes into account, so not exactly trivial to make fairly], or [better] funding vs accuracy comparisons) supporting this idea that under-funding is a substantial factor affecting the accuracy of US state-level polls?
(N.B. I've also asked this on politics SE, but it doesn't seem to be an interesting question for that audience... and the gist of the question seems suitable here as well, even if it's not a definitive claim as to the [main] cause. So a correlational answer would be quite acceptable.)