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Justice Ruth Bader Ginsburg knows an opportunity when she sees one.

Last Friday night at the close of business, she wrote a statement in which she was joined by Justice Stephen Breyer suggesting that the controversial Citizens United case should be revisited.

Citizens United held that the government cannot ban campaign spending by corporations in elections.

Ginsburg had voted against Citizens United in 2010, and in Friday's statement she was signaling that a new case might give the court the opportunity to look at Citizens United again.

The statement did not come out of the blue.

Last December the Montana Supreme Court issued an opinion that appears to directly contradict Citizens United, upholding  a Montana law that prohibits campaign expenditures by corporations. Opponents of the decision asked the U.S. Supreme Court in Washington to step in and block the Montana decision.

"If Montana is allowed to flout this court's holdings in Citizen's United in such a willful and transparent fashion, respect for the Constitution, the rule of law, and this court will be eroded," wrote James Bopp, a lawyer for plaintiffs challenging the Montana ruling.

The Supreme Court did step in at 6 p.m. on the eve of a three-day weekend to put a temporary hold on the Montana Supreme Court's ruling. Ginsburg agreed with the decision. "Because lower courts are bound to follow this court's decisions," the stay was necessary, she said.

But then she went further.

Ginsburg and Breyer (another Citizens United dissenter) said in a statement attached to the court's order: "Montana's experience, and experience elsewhere since this court's decision in Citizens United v. FEC makes it exceedingly difficult to maintain that independent expenditures by corporations 'do not give rise to corruption or the appearance of corruption.'"

She quoted a key part of the Citizens United decision.

Ginsburg, of course, recognizes that the five justices who ruled in favor of Citizens United still sit on the bench.

Fred Wertheimer, president of Democracy 21,who is a fierce critic of Citizens United, explains  her strategy.

"If the court takes this case, it will create the opportunity on the highest legal stage to present a compelling case to the Supreme Court that it was dead wrong in the Citizens United decision. That may not convince the five justices who decided the case to change their opinion, but it will be part of building the case that will ultimately prevail that Citizens United was wrongly decided and must be reversed."

Ginsburg references the current state of affairs in elections. She says, "in light of the huge sums currently deployed to buy candidates' allegiance " the Court should have the opportunity to explore whether Citizens United "should continue to hold sway."

Even though the Supreme Court granted the temporary stay, it does not mean that the court will automatically take up the case and hold hearings. It could "summarily reverse" and send the case away without merit briefs or arguments.

Tom Goldstein, publisher of the influential ScotusBlog, says that the court could summarily reverse a decision with only five votes, but a different "rule applies when four justices are willing to vote for plenary review - i.e., the "four votes to grant" rule takes precedence over the "five votes can summarily reverse" rule.

While the majority of the Montana Supreme Court distinguished its case from Citizens United by saying that the Montana case "concerns Montana law, Montana elections and it arises from Montana history" Justice James C. Nelson dissented.

Nelson said that while he "thoroughly" disagrees with Citizen's United, "the fact remains that the Supreme Court has spoken."

"Like it or not, Citizens United is the law of the land as regards corporate political speech. There is no 'Montana exception," he said.

"The Supreme Court could not have been more clear in Citizens United v. FEC: Corporations have broad rights under the First Amendment to the United States Constitution to engage in political speech, and corporations cannot be prohibited from using general Treasury funds for this purpose based on antidistortion, anticorruption  or shareholder-protection interests," Nelson wrote.

Two years after the Citizens United case, those on opposing sides seemed to be getting even further apart when it came to the issue of campaign finance. But Ruth Bader Ginsburg is laying down a marker.