Only allow money to be donated to a candidate from the voting district that elects them or their party affiliation organization. PACTs would have to register and reside in that specific district, not general money from anywhere. City election means money only from city residents that can prove they can vote in that city. No outside money. The money follows the votes.
State money follows state voters, and so on. National money to national elections.
State money follows state voters, and so on. National money to national elections.