> Shockingly (or not), I expect the vast majority of U.S. politicians would say that's exactly how they behave.

Except I've never once seen such a claim actually made by any politician. So at the very least it seems likely to stand out.

And as for how to believe them: "I intentionally have no access to the donor list, I have never seen the donor list, and if you tell me you've donated to my campaign I will have no particular reason to believe you, so don't bother".