Such a change would elate conservatives frustrated by Washington’s growing web of agencies and regulations — too often untethered, they say, from any specific directions from Congress. But liberals counter that long-abandoned legal theories shouldn’t block elected leaders and their appointees from meeting challenges and carrying out the will of the voters.

“Without question a 6-3 Court captured by right-wing and corporate interests could shut down much of the progressive agenda, if it could act with impunity,” said former Sen. Russ Feingold (D-Wis.), president of the progressive legal nonprofit the American Constitution Society. “Clean water, clean air, food and drug safety, regulation of the health care and health insurance industries, consumer protections and workers’ rights (up to and including the right to organize) are all on the chopping block in that scenario.”

Nicholas Bagley, a law professor at the University of Michigan, said expanding the court’s existing five-person conservative bloc makes it all the more likely for once-unorthodox views of government power to prevail.

“The thing that’s different with a 6-3 court versus a 5-4 court is you’ve just got a bigger margin for crazy,” Bagley said, noting that the outcomes of several high-profile Supreme Court cases in recent years have flipped because of just one conservative defection. “I just think that people underestimate dramatically the aggressiveness and zealotry of the conservative legal movement.”