The U.S. Supreme Court should seize the opportunity to reverse its misguided 5-4 decision in the Citizens United case, a ruling that has introduced unprecedented corporate and special interest spending into the presidential campaign, distorting the election process and inviting corruption. It will take only one changed vote to correct that mistake. The most likely switch is Justice Anthony Kennedy.

Last month the Montana Supreme Court rejected the underpinnings of the Citizens decision. By a 5-2 vote it upheld a century-old Montana anti-corruption law banning political expenditures by corporations. That state long ago learned the hard lesson that when corporations can buy candidates they also buy power. A century ago the so-called "Copper Kings" controlled elected officials in Montana and made sure they did the bidding of the mining industry.

In upholding Montana's law, that state's high court found itself in direct conflict with the Citizens ruling, which concluded that any laws limiting spending by corporations and other interest groups violated the Constitution's free speech protection. The U.S. Supreme Court had no choice but to order a stay of the Montana ruling, given the state court's refusal to follow the high court's precedent.

U.S. Supreme Court Justice Ruth Bader Ginsburg, joined by Justice Stephen Breyer, is asking her fellow justices to use the Montana case to reconsider Citizens.

"Montana's experience, and experience elsewhere since this Court's decision in Citizens United … make it exceedingly difficult to maintain that independent expenditures by corporations 'do not give rise to corruption or the appearance of corruption.' A petition (to hear the Montana case) will give the Court an opportunity to consider whether, in light of the huge sums currently deployed to buy candidates' allegiances, Citizens United should continue to hold sway," wrote Justice Ginsburg.

The conclusion that allowing corporate money to flow unhindered into election campaigns would "not give rise to corruption or the appearance of corruption" was critical to the Citizens decision. If a majority of justices, when considering the Montana case and what has happened since their Citizens ruling, conclude that out-of-control campaign contributions do give rise to corruption and the appearance of corruption, that could trump the free speech argument and lead the court to reverse, or at least moderate, the Citizens decision.

The people of Montana know that unregulated corporate campaign money can corrupt a government. It's why the Supreme Court there stood by the state's law. And we are seeing how corruptive super-PAC money is on federal campaigns. Super Political Action Committees may now raise unlimited sums of money from corporations, unions, associations and individuals to advocate for or against political candidates.

According to the Center for Responsive Politics, 332 groups organized as super PACs have reported total receipts of $98.7 million and total expenditures of $51.2 million in the 2012 election cycle. In the Republican presidential primary, Restore Our Future has raised $30.2 million to back Mitt Romney; Winning Our Future has invested $9.8 million in Newt Gingrich; and the group Red, White & Blue has spent $3.12 million on Rick Santorum.

With the Citizens decision eliminating limits on individual contributions, individual magnates are donating staggering amounts. It's not hard to conclude who will hold sway in a Romney administration, considering that $5 million of the pro-Romney Restore Our Future money came from just 25 tycoons and corporations, including $500,000 each from Oklahoma mining executive Joseph W. Craft and billionaire hedge-fund mogul Bruce Kovner.

Typically the campaigns use super-PAC money to purchase voluminous negative attack ads, often full of distortions, to try to destroy an opponent, a tactic Mr. Romney has frequently employed. In writing the majority opinion, Justice Kennedy stated these super PACs should remain independent of the candidates. In reality, former campaign aides staff many of the PACs, well versed on campaign strategies. These groups also lack the transparency Justice Kennedy expected.

The spending and corruptive influence will grow as the campaigns move to the general election.

President Obama, who rightly criticized the Citizens decision, has effectively sold out, signaling his campaign will cooperate and benefit from friendly super PACs. Obama campaign officials say they had no choice if they hoped to compete. We would have preferred the president stood on his principles.

Citizens was a terrible decision that has put our democracy up for sale. The Supreme Court should reverse it and again allow the use of reasonable campaign spending limits.