> In practice, Citizens United obviated any US regulations on political advertising. A rich patron can pour as much money as s/he desires into advertising on behalf of a campaign, and we don't have a right to know who that person is.

No, Citizens United didn't do that. That right always existed. If you're a billionaire, you always could purchase TV ads that feature (for example) you talking about how great Candidate Foo is, and why Candidate Foo will be the best thing since sliced bread. That is a fundamental right of free speech in our democracy - the government cannot restrict you from praising or criticizing a candidate. They can restrict you from coordinating with the candidate to make those statements, but they can't restrict you from your own independent speech.

The Citizens United decision ruled that people preserve this right when acting as a group. So instead of one single billionaire purchasing ad spots, a group of people could pool their money and purchase the ad time instead. Or they could launch a crowdfunding campaign. All of that is still perfectly legal as long as the person (or people) running the ads aren't coordinating their efforts with the candidate and the candidate's campaign.