The Citizens Clean Elections Act, passed by voters in a 1998 ballot initiative, gave candidates extra money if they face well funded opponents that opted out of the state election financing system.

Candidates also could qualify for greater public financing based on political spending by independent political groups that ran advertisements opposing their candidacy or supporting other candidates.

Chief Justice John Roberts wrote “laws like Arizona’s matching funds provision that inhibit robust and wide-open political debate without sufficient justification cannot stand.”