NRA, among others, primarily fundraises over the phone. The mass scam calling and automated calling trains people to ignore calls from unfamiliar numbers. This has likely already lead to a drop in the number of accepted calls and donations to the NRA et al. One way we could prove this is politically targeted: FOIA request government records on scam call reports (or use public sites that report them) and then cross reference those names and numbers to political donations. I bet the bulk of scam calls are going to nra members and conservatives. This should also be relatively straightforward to prove too.