The Supreme Court decision striking down public matching funds in Arizona’s campaign finance system is a serious setback for American democracy. The opinion written by Chief Justice John Roberts Jr. in Monday’s 5-to-4 decision shows again the conservative majority’s contempt for campaign finance laws that aim to provide some balance to the unlimited amounts of money flooding the political system.

In the Citizens United case, the court ruled that the government may not ban corporations, unions and other moneyed institutions from spending in political campaigns. The Arizona decision is a companion to that destructive landmark ruling. It takes away a vital, innovative way of ensuring that candidates who do not have unlimited bank accounts can get enough public dollars to compete effectively.

Arizona’s campaign finance law provided a set amount of money in initial public support for candidates who opted into its financing system, depending on the type of election. If a candidate faced a rival who opted out, the state would match the spending of the privately financed candidate and independent groups supporting him, up to triple the initial amount. Once that limit is reached, the publicly financed candidate receives no other public funds and is barred from using private contributions, no matter how much more the privately financed candidate spends.