Outlaw lobbyist donations from corporations and individuals.
Make meetings that politicians have with corporations and wealthy citizens publicly recorded and openly available without censorship.
Audit government employee accounts monthly, or even weekly, to prevent personal donations and transfer of funds.
Military personnel are not allowed to collect rewards or donations while they are serving. The same rule should apply for government politicians.
You do a job, and you get paid for it. You have no legal reason to accept private/personal donations from any company or wealthy citizen.