The Supreme Court’s Monday ruling to strike Montana’s ban on corporate campaign spending opens a new chapter in the political money wars, fueling an improbable but increasingly vocal movement to amend the Constitution.

“This Supreme Court ruling could be a watershed in terms of the court aligning itself with the interests of big corporations,” said Jamie Raskin, a Maryland state Senator and law professor at American University’s Washington College of Law. “And the constitutional amendment strategy will be a way to plant the flag and rally people for a different vision of the Constitution and the country.”

More than a dozen Members of Congress have proposed various constitutional amendments in the wake of the Supreme Court’s Citizens United v. Federal Election Commission ruling to deregulate corporate and union political spending. Some declare that corporations are not people; others empower Congress and the states to restrict campaign spending and contributions.

Until now, such proposals have garnered little notice, given the slim likelihood that any could clear the high bar set for amending the Constitution: a two-thirds majority in Congress and ratification by at least 38 states.

But the court’s 5-4 ruling in the Montana case, known as American Tradition Partnership Inc. v. Bullock, makes crystal clear that an amendment is needed, watchdogs say.

Monday’s ruling “underscores the need for a constitutional amendment since there’s no prospect of this court undoing the damage it’s done,” said Robert Weissman, president of Public Citizen, which is helping lead a state and local campaign to pressure Congress to amend the Constitution. “And if we take seriously how consequential is that damage, then we need an amendment to remedy it.”

Hawaii, New Mexico, Vermont and Rhode Island have already approved resolutions supporting constitutional amendments aimed at reversing Citizens United. Massachusetts and California are scheduled to vote on similar resolutions as early as Thursday.

More than 200 such measures have been enacted at the local level. A coalition of more than 60 progressive, labor and environmental groups has also mounted local protests and state ballot initiatives around calls for an amendment.

“It’s going to be very difficult for Congress to ignore that momentum in the states,” said John Bonifaz, executive director of Free Speech for People, which is helping lead the campaign. He noted that past Supreme Court rulings have been overturned via constitutional amendment in seven cases, including the 19th Amendment, which gave women the right to vote.

Conservatives reject such proposals out of hand.

The amendments on the table are patently unconstitutional and would rob civic groups, soccer leagues and churches of their basic right to associate and speak out, say scholars at the Center for Competitive Politics. Polls show that the segment of the public believing the First Amendment does not go too far reached a high of 79 percent last year, noted President David Keating, citing a 2011 survey by the First Amendment Center.

“I don’t see Congress passing it,” Keating said. “And even if it did, I don’t see three-quarters of the states ratifying it. It’s just too dangerous a concept.”

If nothing else, the Montana ruling throws into stark relief the sharply divergent options facing Congress and the courts as they respond to the wave of unrestricted spending unleashed by Citizens United. Reform advocates on and off Capitol Hill lobbied the Supreme Court to take up the Montana case to revisit and rehear Citizens United. By summarily rejecting the Montana ban, the high court majority signaled that it remains firmly in the deregulation camp.

Far from clearing the way for new campaign finance restrictions, the Supreme Court might well lift political money limits still further, given the precedents set in Citizens United. Presumptive GOP presidential nominee Mitt Romney and some Republicans on Capitol Hill have called for an end to existing limits on contributions to parties and candidates, one of the few remaining election laws on the books.

Republicans have also mounted a campaign to discredit Democratic-authored disclosure legislation as an invitation to harassment and an assault on free speech. And additional campaign finance challenges, many of them led by activist Indiana lawyer James Bopp Jr., are wending their way through the courts.

“America has to wake up to the fact that there is a conservative legal and judicial movement afoot to wipe out all campaign finance laws, and James Bopp is very clear about that,” said Raskin, who authored a letter asking Congress to consider a constitutional amendment that has been signed by a majority of Maryland’s state legislators.

To Raskin, that makes the case for a constitutional amendment all the more urgent. Some on Capitol Hill agree. Following Monday’s ruling, several Democrats who have either authored or co-sponsored constitutional amendments issued statements saying they would now redouble their efforts. That includes Rep. Adam Schiff (D-Calif.), the most recent federal lawmaker to propose an amendment to permit limits on political money.

Instead of revisiting Citizens United, “the court doubled down on its flawed decision,” Schiff said. “Regrettably, this makes a constitutional amendment — such as the one I introduced last week — all the more necessary.”