Missouri Gov. Jay Nixon endorsed campaign finance reform proposals today.

The governor said requiring candidates to depend on small donors would force candidates to build “a broad base of support” and would serve as “a good check to corruption.”

Even so, Nixon acknowledged that new limits couldn’t touch “independent expenditures.” Individuals and groups can spend unlimited amounts to promote or oppose candidates, so long as the expenditures aren’t coordinated with the candidates who benefit.

Courts have said independent expenditures are covered by the First Amendment right to free speech.

Nixon was the named plaintiff in Nixon v. Shrink Missouri Government PAC.