This week’s Supreme Court argument on abortion has accelerated an urgency among Senate Democrats to fundamentally alter how the court operates, fueled in part by lingering anger over Republican confirmation maneuvers that have led to three new conservative justices in the past four years.

Few senators as of yet are fully endorsing ideas like mandatory retirement for the justices or expanding the number of seats on the nine-person court. But a growing faction, long hesitant to embrace structural changes, say they are now prepared to consider such moves.

That sentiment is growing among Democratic senators, according to interviews with more than a third of the 50-member caucus Thursday, even as President Biden has shown little indication that his resistance to overhauling the Supreme Court has softened.

While changing the composition of the court may sound radical, it's actually already been done. (Drea Cornejo, Adriana Usero, Daron Taylor/The Washington Post)

Sen. Brian Schatz (D-Hawaii) said many Democratic senators have been reluctant to entertain proposals about changing the Supreme Court in the past because “we do respect the separation of powers under the Constitution.”

But Wednesday’s oral arguments, in a case involving a Mississippi law that would bar most abortions after 15 weeks, changed those sentiments, he said. “It is hard to watch that — and I did watch a fair amount of it — and not conclude that the court has become a partisan institution,” Schatz said. “And so the question becomes, well, what do we do about it? I’m not sure. But I don’t think the answer is nothing.”

Sen. Elizabeth Warren (D-Mass.) made a similar point. “What happened yesterday forces all of us to rethink our views about the makeup of the court,” she said. Referring to justices who appeared prepared to overturn precedent and scale back abortion rights, Warren added, “They‘ve undermined confidence in the court and force us in Congress to rethink how to build a court that the American people can trust.”

A Supreme Court review of a Mississippi abortion law could pave the way for many other state laws that restrict or ban the procedure. (Joshua Carroll/The Washington Post)

In one sense, elected officials are starting to catch up to the progressive Democratic base which, in recent years, has loudly advocated for overhauling the structure of the Supreme Court. These rank-and-file Democrats have been motivated largely by anger against Senate Minority Leader Mitch McConnell (R-Ky.), whose maneuvering the last four years successfully installed three conservative justices, two of whom replaced Justices Anthony M. Kennedy and the late Ruth Bader Ginsburg, who were favorable to abortion rights.

When Justice Antonin Scalia died in February 2016, McConnell, then majority leader, took the unprecedented step of refusing to consider President Barack Obama’s nominee, holding the seat open until President Donald Trump could fill it upon taking office with Justice Neil M. Gorsuch.

And when Ginsburg died shortly before Trump’s term ended, McConnell changed tactics and pushed through Justice Amy Coney Barrett with unusual speed. Those two justices — along with Justice Brett M. Kavanaugh — have cemented a conservative majority that now appears poised to significantly cut back abortion rights.

Republicans contend that Democrats are threatening to overhaul the high court solely because they dislike its opinions, calling that a dangerous attack on judicial independence. They dismiss complaints that anything was wrong with the recent confirmations, saying that is sour grapes by Democrats because events have not gone their way.

Sen. Mike Lee (R-Utah), responding earlier this year to a Democratic bill to expand the court, tweeted that “packing the court is an act of arrogant lawlessness” and added, “Those behind this effort spit in the face of judicial independence.”

Democrats are driven in part by what they see as contradictions between what Supreme Court nominees tell senators during their confirmation hearings and their actions on the bench once they have secured a lifetime appointment.

A particular point of contention this week was comments from Kavanaugh, who said pointedly during the oral argument that the Supreme Court had overturned long-standing precedents in the past, including in Brown vs. the Board of Education, which found that segregation of public schools was unconstitutional.

For Democrats, that was at odds with his tone during his bruising confirmation fight in the Senate three years ago, when he assured senators that he believed Roe vs. Wade, the landmark 1973 case that established a constitutional right to an abortion, was settled law.

“Kavanaugh’s cavalier talk yesterday about precedent, and the clear political motivations of the plaintiffs in this case, are going to undermine faith in the judiciary,” Sen. Chris Murphy (D-Conn.) said. “We’ve got to think about ways to sort of depoliticize the courts. And one of the ways to do that is to make sure that no one president gets to stack the bench.”

Sen. Richard Blumenthal (D-Conn.) said lawmakers should seriously consider term limits or mandatory retirement for the justices. Some other courts, Blumenthal noted, have similar restrictions for their judges.

Other Democratic senators pointed to judicial ethics as one area of particular concern, noting that justices essentially police themselves and face no accountability to the public for their actions.

“I’m not ready to say we need to change the number of justices,” Sen. Jeanne Shaheen (D-N.H.) said. “But I do think this is a different era. And we need to take a look at how the court functions.”

There remains, however, a massive gulf between a fulsome debate about structural changes to the Supreme Court and actual enactment of such ideas.

For one thing, the Senate would almost certainly need to dismantle the filibuster — which requires a 60-vote threshold for most legislation to advance — to push through revisions. And experts say it’s an open question whether term limits for justices can be imposed through legislation or would require a constitutional amendment.

“Even if you could do term limits, if you could do it tomorrow, it doesn’t help pregnant people in Texas right now, or in Mississippi or across the country. It doesn’t help Black voters in Georgia,” said Christopher Kang, co-founder and chief counsel of Demand Justice, a liberal advocacy group that focuses on the judiciary. “The only thing that is actually going to provide balance to the court and do something in the near term is Supreme Court expansion.”

During the 2020 presidential campaign, several Democratic candidates, though not Biden, embraced the notion of expanding the court. That marked a notable shift of opinion on “court-packing,” which long had a negative connotation stemming from Franklin D. Roosevelt’s failed 1937 effort to add as many as six justices.

Candidate Pete Buttigieg, now secretary of transportation, suggested increasing the number of justices to 15 — five selected by Democrats, five by Republicans and five chosen by the other 10.

In response to such calls for change, Biden, who has made his reservations about them clear, assembled a commission shortly after taking office that is tasked with reviewing various proposals. It meets again next week and will prepare a final report to Biden later this month.

“If you look at the history of the Supreme Court, it was important to the president to have a range of viewpoints that he could look at and assess and look at the historic nature of a lot of these issues,” White House press secretary Jen Psaki said.

Perhaps the most controversial of the proposed Supreme Court changes is increasing the number of justices. Sen. Edward J. Markey (D-Mass.), Rep. Jerrold Nadler (D-N.Y.) and other Democrats introduced a bill in April to expand the size of the Supreme Court to 13 justices.

Sen. Tina Smith (D-Minn.), a former executive at Planned Parenthood in Minnesota, endorsed Markey’s bill in September. She said she was motivated to embrace changes to the Supreme Court partly by its decision earlier this year to keep intact a restrictive new abortion law in Texas.

“Yesterday, we saw the court is politicized. The question is, what are we going to do about it?” Smith said Thursday. “Are we going to take action to rebalance the court, or are we just going to sort of bury our heads in the sand and pretend that it hasn’t happened?”

Still, senators appear more likely to consider term limits rather than court expansion. That broadly reflects public sentiment; a Marquette Law School poll from November found that 48 percent of American supported increasing the number of justices on the Supreme Court, while 52 percent were opposed.

In contrast, 72 percent favored fixed terms for Supreme Court justices, rather than lifetime appointments, compared with 27 percent of adults who opposed them.

Not all Democratic senators interviewed Thursday embraced the idea of far-reaching changes to the Supreme Court.

Sens. Amy Klobuchar (D-Minn.) and Christopher A. Coons (D-Del.), both members of the Judiciary Committee, either deferred to the ongoing review by Biden’s commission or said discussions of changes to the court would have to wait until the impact of this term’s decisions were evaluated.

Others oppose the proposed changes outright.

Sen. Joe Manchin III (D-W.Va.) emphasized Thursday that he did not support enlarging the Supreme Court but said he has not considered other options, such as term limits for justices. But Sen. Jon Tester (D-Mont.) said flatly that he did not support changes such as term limits or mandatory retirement for justices.

“Where does this stuff stop, okay?” Tester said. “I just think mandatory retirement gets into a bigger problem.”