Not to get too into it, but…
Why don’t we just simply disallow all public campaign finance? You can’t accept money from anyone for any reason. Campaigns are financed from a general fund, and capped at a reasonable number like 10m for presidential candidates. You must get enough signatures to be on the ballot, and once you’re on you have access to the money. Every dollar must be accounted for. No campaign spending except from the general fund.
Once you’re elected, no gifts, no dinners, no favors, no nothing. You can’t accept anything from anyone. Nor can your immediate family.
Once you leave your office, you cannot work in any field or industry for which you sponsored or co-sponsored legislation earning more than 50k/yr total compensation for 10 years. You cannot earn more than what you earned in office in any of those ten years for all income combined.
You cannot become a lobbyist for 10 years after holding office.
Our government is bought and paid for. Until we completely remove the ability for politicians to benefit financially from serving corporate interests, they will continue to do so.
Removing all private campaign finance provides powerful disincentives to those who would benefit from trading money for public policy. Politicians should have very very strict limits on how they benefit from their tenures as public servants, and for years afterwards as well because the possibility for conflicts of interest is so high, and the consequences so great.