>I’d personally be fine with restrictions on where funding for political organizations comes from (although I’m not sure how you make that compatible with the 1st amendment)

Despite what the proponents of Citizen's United might have us believe, money != speech, and adding restrictions to political donations is perfectly compatible with the first amendment.

Would-be donors are allowed to advocate for political positions just the same as anybody else. Nobody is stopping them. That would still be the case with donation limits. They can still get on TV and argue their case.

There is already a precedent for limiting donations. Try donating money to ISIS or Hezbollah and see if the government considers that an exercise of your first amendment rights.