The test case for tanking this behaviour seems almost too easy to set up. Pick a series of organisations across the political spectrum. Think tanks, civil rights outfits, charities, et cetera. (Nothing explicitly partisan.) Overzealously document a donation to each, have them each confirm their acceptance in writing and then settle each donation in cash via FedEx.

(Round 2, donating to candidates via cash the cops steal, is more tricky to set up since you'd need separate donor-candidate pairs across the partisan spectrum to make it work well.)