Give all candidates and referendums free, equal and fair time on broadcast television stations to make their cases, but restrict all other forms of advertising by or on behalf of the candidates or referendums.
Too much money is wasted on advertising that voters find weary and often turns negative. Lobbyists believe that those who spend the most on advertising will control the message and influence voter outcome - break this cycle.
I am aware of the Bipartisan Campaign Reform Act of 2002 / McCain-Feingold bill ( http://www.lawpublish.com/political-advertising.html) - I don't know if this should be rewritten or replaced, but it seems that if the FCC can control foul language on television and radio, it should be able to make this happen.