Precedent actually started with Buckley v. Valeo when the Supreme Court found some aspects of the Federal Election Campaign Act of 1971 unconstitutional, and ruled that we have a constitutional right to spend money in the political process because money equals speech (although here the court acknowledged that too much money could lead to corruption, so they upheld a limit on individual contributions to a candidate). The court also set the foundations for Citizens United by striking down limits on any interdependent entity to spend money to influence and election. As long as the efforts are not coordinated with a campaign, the speech is constitutionally protected as political and cannot be limited. Btw, Political speech here defined as speech that says "vote for," "dont vote for," "elect," "deny," any call to action. This is different from 'Issue Ads', or ads that say "Obama is a terrible person." I think this last bit is one of the more important issues since these ads are completely outside of the regulations that Citizens United was challenging.