Less than a year after the controversial Citizens United ruling, the Supreme Court is expected to rule against an Arizona law that seeks to moderate election spending by providing subsidies to candidates who face big-spending opponents.

On Monday, the Supreme court announced it would hear a challenge to the Clean Elections Act, a law adopted by Arizona voters in 1998 that is designed to limit campaign spending by providing public funding to candidates.

Candidates can opt out of the public funding to avoid its pre-set spending limits, but by doing so they may be inadvertently helping their opponent. If a candidate opts out of the public funding, and receives private funding above the pre-set limit, the state provides "matching" public funds to the other candidates.

The court has already signaled its disapproval of the legislation. In June, it blocked the state from providing "matching funds" to candidates running for office.

The law is being challenged by libertarians who claim it unfairly punishes candidates who raise private money by forcing them to cut back their spending in order to avoid their opponent receiving additional public funds.

The court is set to hear arguments for McComish v. Bennett in the spring.

"Public financing has a number of benefits, including reducing the threat of corruption and the appearance of corruption, providing a jump start for new candidates who are not professional politicians, and freeing up candidates and officeholders to have more time to interact with voters," Richard Hasen of the Loyola Law School in Los Angeles said. "The whole point of the extra matching funds in the Arizona plan is to give candidates assurance they won't be vastly outspent in their election."

"While an adverse ruling by the Supreme Court in McComish would not mean that all public financing systems would be unconstitutional, it would eliminate one of the best ways to create effective public financing systems," Hasen added.

Those challenging the Clean Elections Act have an important precedent on their side. In 2008, the Supreme Court struck down the "millionaire's amendment" in the McCain-Feingold campaign finance act that allowed candidates to accept larger contributions if they faced an opponent who was spending large sums of private money. The court ruled that the attempt to equalize campaign spending violated the First Amendment.

"We're ecstatic that we have a chance to put an end to the worst features of taxpayer subsidies for politicians," Clint Bolick, a lawyer for the Goldwater Institute in Phoenix, said. "The matching-funds system brazenly violates the First Amendment right of candidates to speak without having government put its thumb on the scale for their opponents."

In January of 2010, the Supreme Court struck down another provision of the McCain-Feingold campaign finance act in its ruling on Citizens United v. Federal Election Commission.