The nation's high court this morning voided a key provision of the state's system of public financing of elections, potentially crippling the 13-year-old system.

In a divided decision, the U.S. Supreme Court said Arizona cannot provide additional funds to publicly financed candidates when their privately financed foes spend more. Also gone are provisions which give extra money when independent committees run commercials against them.

Technically speaking, the Clean Elections Act still exists and candidates are still able to get public dollars if they agree not to take outside funds. And the court was careful to say that its ruling does not make public financing by itself illegal.

But even the executive director of the Citizens Clean Elections Commission said that the demise of the matching funds will result in fewer candidates agreeing to have their campaigns publicly finance. Todd Lang said that candidates who face well-financed foes are unlikely to opt for public dollars knowing that they would be outspent, with no way to make up the difference.

Chief Justice John Roberts, writing the majority ruling in the 5-4 decision, accepted the arguments by foes that the "matching funds'' provision violated their constitutional rights of free speech. That is based on the argument that they will not spend money on their own behalf, or on behalf of a candidate they support, knowing that every dollar they spend means an extra dollar for the person they do not want elected.

But Justice Elena Kagan, in her dissent, said the system — including the matching funds — is a legitimate exercise of state power to deal with "the cancerous effect of corruption'' of campaign dollars being traded for political votes.

Under the terms of the 1998 voter-approved law, candidates who agree not to take outside funds get a set amount of public dollars based on the office being sought.

In the case of governor this past election, the state provided $707,447 for primary races and another $1,061,717 for general election survivors. But the law provides a match, up to three times the original amount, when foes — or those acting on their behalf — spend more.

In 2009, U.S. District Court Judge Roslyn Silver ruled the provision unconstitutional based on those First Amendment arguments.

The 9th U.S. Circuit Court of Appeals, however, said challengers of the matching funds provision did not prove that candidates or independent groups stopped spending for fear of helping those they wanted to defeat. That led to the review by the high court.

In the majority decision, Roberts noted that the court previously threw out a federal law which said once a candidate spends more than $350,000 of his or her own money, then political foes could take more in contributions from individuals. In that case, the chief justice noted, the court concluded the provision forced candidates to choose between their First Amendment rights — with the right to spend money on one's own behalf within that right — and being subject to discriminatory funding limitations.

The Arizona law, Roberts argued, is even more legally offensive.

At least in the prior case, the other candidate still had to go out and solicit new donations. In Arizona, however, the state handed the extra money to the outspent publicly funded candidate.

Roberts also said the fact that the match applies to independent expenditures — those made by an outside group, with no connection to the publicly funded candidate's foes — also makes the Arizona law unconstitutional. That's because the publicly financed candidate gets to spend the state-provided cash any way he or she wants; the other candidate has no say over the message being sent by what are supposed to be political friends.