WSJ.com:
"The Arizona campaign-finance law, which offered extra public funding to state political candidates who faced well-heeled opponents, was ruled unconstitutional for infringing on Americans' right to express themselves freely in election campaigns.
The opinion, by Chief Justice John Roberts, found that a program that gives matching funds to publicly funded candidates, who agree to limits on their spending and to take part in a candidate debate, was unfair to their privately financed opponents."