In a closely watched ruling that could have implications for state and federal public financing systems, the Supreme Court on Monday struck down a portion of an Arizona law that had offered additional public funds to candidates running against well-funded opponents.

“Arizona’s matching funds scheme substantially burdens political speech and is not sufficiently justified by a compelling interest to survive First Amendment scrutiny,” the majority concluded in a 5-4 ruling in Arizona Free Enterprise Club’s Freedom Club PAC v. Bennett. The provision violated the First Amendment, the high court found.

Reform advocates deplored the ruling but said it will not upend the public financing regime. The ruling will affect states where similar laws regulate the elections of governors and state legislators. However, Congressional public financing legislation introduced on Capitol Hill deliberately leaves out “trigger” provisions such as the one the high court rejected.

“The good news is that this is not the death knell to public financing,” said Bob Edgar, president and CEO of Common Cause. The ruling did not surprise reform advocates, given the high court’s tilt toward deregulation in Citizens United v. Federal Election Commission and other rulings.

“It’s as bad as expected but perhaps not as broad as absolutely feared,” said Tara Malloy, associate counsel at the Campaign Legal Center. She concurred with Edgar that the ruling does not spell the end of public financing, but she added: “It will probably have ripple effects across the other states that have programs similar to Arizona, including trigger provisions.”

But Senate Minority Leader Mitch McConnell praised the court’s decision. “Today the Supreme Court ruled that a state cannot use taxpayer funds to punish a successful political campaign, overturning a 9th Circuit decision,” the Kentucky Republican said in a statement. “This was a case that went to the very heart of free speech liberties and the court’s disapproval of legislative favoritism. The high court has already ruled that penalties on political spending infringe on fundamental First Amendment rights. It was the view of the Supreme Court, which I share, that the Arizona statute substantially impinges on the fundamental right to engage in political speech without the government penalizing someone for it.”

Some legal experts have warned that without trigger provisions for candidates facing deep-pockets opponents, public financing systems in states such as Arizona, Connecticut and Maine would be less appealing to candidates. But Edgar disagrees: “I think what’s less appealing to people running for public office is spending 20 to 30 hours a week raising money.”

However, he acknowledged that conservatives are poised to challenge any new state public financing laws in court, figuring any such challenges will enjoy a receptive ear at the Supreme Court.