The Supreme Court's ruling Thursday undercutting a ban on corporate political spending that had been in place for more than a century has left abortion-rights supporters jittery that the justices could be similarly prepared to upend the landmark Roe v. Wade decision the court handed down 37 years ago this week.

"Yesterday's Roberts court decision, which exhibited a stunning disregard for settled law of decades' standing, is terrifying to those of us who care deeply about the constitutional protections the court put in place for women's access to abortion," said Nancy Northup of the Center for Reproductive Rights. "We are deeply concerned. ... Yesterday's decision shows the court will reach out to take an opportunity to wholesale reverse a precedent the hard right has never liked."

"It is worrisome beyond the direct impact of yesterday's ruling on election law," said, Jessica Arons, the director of the Women's Health and Rights Program at the Center for American Progress. "It's certainly cause for concern."

Critics said the court's 5-4 ruling in the Citizens United case Thursday declared unconstitutional a law which has been in place since 1907 barring corporations from involvement in federal elections. Just six years ago, the Supreme Court called the longstanding ban "firmly embedded in our law." Now, it's gone.

Abortion rights advocates said the willingness of the court's majority to toss aside precedent undercut Chief Justice John Roberts's assurances at his confirmation hearings in 2005 that he would tread lightly when it came to rulings like Roe v. Wade.

"It's settled as a precedent of the court, entitled to respect under principles of stare decisis," Roberts said then. "To avoid an arbitrary discretion in the judges, they need to be bound down by rules and precedents. ... I do think that it is a jolt to the legal system when you overrule a precedent. Precedent plays an important role in promoting stability and evenhandedness."

"Yeah, it's settled law - until you get enough votes in your favor," Arons scoffed Friday. "Then it's, 'We respect precedent, but we still overturn it.'"

A lawyer who regularly argues before the Supreme Court, Tom Goldstein of Akin Gump, said the abortion rights supporters were right to be worried in the wake of Thursday's decision.

"Some of the Supreme Court doesn't like some of the court's O'Connor-era abortion jurisprudence just like they don't like some of the O'Connor-era jurisprudence on campaign finance," Goldstein said. "Abortion is one of the areas where there is a long string of cases conservatives believe is totally misguided."

Goldstein said the campaign finance decision indicates that the court is increasingly willing to break with previous precedents when it comes to "the really central questions of constitutional law," which include abortion, gay rights, the death penalty and church-state issues.

"Those are questions I think the court thinks you just have to get right. Just because someone else got there first doesn't give it any greater claim to legitimacy," Goldstein added.

Abortion rights advocates said they were unsettled not solely by the court's 5-4 holding in the Citizens United case, or by the majority's dismissive approach to laws considered well-established, but by the unusual procedural steps the court took to tee up the ruling it issued Thursday.

In the district court, Citizens United dropped its arguments for overturning the corporate spending ban and asked that the case be resolved on narrower grounds. However, after the case was first argued at the Supreme Court, the justices ordered the parties to return and present new arguments about striking the overall ban. Additionally, the justices' ruling Thursday also explicitly overruled a case decided 20 years ago, Austin v. Michigan Chamber of Commerce, in which the court held, 6-3, that states could bar corporations from involvement in political campaigns.

"It seems like they were looking for any opportunity and as soon as they got one, they were not satisfied to do this incrementally. They wanted to do it all at once," Arons said. "There is concern in reproductive rights circles that if it's something conservative justices feel strongly about, well, now they have the votes to do that."

A supporter of the court's campaign finance ruling, Jeff Patch of the Center for Competitive Politics, said the claims that the court had overturned a century of precedent were exaggerated. He noted that the 1907 law critics referred to was a statute, not a court ruling, and that it banned direct donations to political campaigns--not the independent expenditures the court addressed Thursday.

Abortion opponents were heartened by the boldness of the court's ruling Thursday.

"Where they disagree with the precedent and they think it's wrong constitutionally, they're not afraid to say it," said the American Center for Law and Justice's Jay Sekulow, an attorney who has argued church-state and campaign finance issues before the justices. "Where they think the court got it wrong, they're trying to correct that, and from my perspective that's a good thing." An unthinking embrace of precedent would have protracted the effect of widely reviled rulings like the Dred Scott decision on slavery and the Plessy v. Ferguson decision upholding separate-but-equal treatment of the races, Sekulow said.

Despite the signals that may have been sent Thursday, analysts on both sides of the issue said they still think an explicit repudiation of Roe v. Wade isn't in the cards anytime soon. However, they said the tone and circumstances of the election law decision suggest the court won't be skittish about cutting Roe back even further.

"It's just being held up by a little camel stick," said Janet Benshoof, a longtime abortion rights lawyer. "You're talking to someone who considers Roe v. Wade to have been overturned already," she said, referring to a series of rulings in recent years upholding restrictions on abortion. "It's no longer a fundamental right. We have 300 to 400 criminal laws on abortion that wouldn't be legal under the [original] version of Roe v. Wade."

The majority opinion Thursday was written by Justice Anthony Kennedy, who has expressed support the central holding of Roe v. Wade but has also endorsed state efforts to regulate abortion.

Northup said she thinks laws limiting abortion will multiply further as activists learn of Thursday's decision.

"This is going to be an invitation to folks who want Roe v Wade overturned to continue their push for restrictive state laws so they can get up before the court," Northup said. "Everything is up for grabs."