The only grounds for compelling disclosure is to prosecute a crime, and the Fifth Amendment forbids doing even that if disclosure might incriminate the witness or even damage his reputation. The argument that general disclosure is needed to prevent or discover bribery or other forms of undue influence is specious. Real bribery is not going to be disclosed in a way that such reports would reveal. There are too many ways to evade detection. All the reports do is make it easier to suppress competition from vulnerable or unpopular candidates and views, which is diametrically opposed to everything we fought a revolution to secure.
Similar considerations apply to statutes limiting the amounts of contributions or expenditures.
Money is press. It is the right to publish that is at stake here, and the right to publish is the right to contract with someone else to publish one's views, including a candidate for public office or an advocacy group. We do it the way it was done when this nation was founded. We do it by arranging things so that someone can get a candidate elected, or a measure adopted, on his or its merits, without expenditures of money being able to affect the outcome. That will not happen unless or until people make the effort to inform themselves and decide who or what to vote for based on information and reason and not on the basis of the repetition of images or sound bites.