WASHINGTON, D.C. >>

For the third time in four years, the Supreme Court heard arguments Monday about a case that would deal a financial blow to public sector unions, a major political force in California and Democratic politics, nationally. And unlike the last two cases, the justices are likely to make a decisive ruling in Janus v. AFSCME, which hinges on the legality of unions fees for nonmembers.

Mark Janus, a public employee in Illinois, sued his home state and local American Federation of State, County and Municipal Employees chapter over the requirement that he pay what are known as “fair share” fees to the union. Those fees help cover the costs of collective bargaining and other union engagement with management, something all employees benefit from. The Supreme Court has already ruled that nonmembers cannot be required to pay for a union’s political activities.

Janus and his legal allies, including the Chicago- based Liberty Justice Center, argue that those “fair share” fees — which are allowed in 22 states, including California — are a violation of his First Amendment rights. When the employer is the government, even negotiations on wages and contracts are inherently political because they affect budgets and other policy decisions, they argued.

If the court rules in Janus’ favor, the public sector unions would lose the money brought in by the “fair share” fees, which in California are worth millions. The new rules would also sap their membership, as workers realize they don’t have to pay union dues at all to benefit from the collective bargaining efforts. Unions that operate in both “right to work” and “fair share” states say the shift could drive down membership by 15 percent to 30 percent.

The top five takeaways from the hourlong session at the U.S. Supreme Court:

1. Gorsuch’s silence was deafening

Justice Neil Gorsuch, the newest member of the Supreme Court, is the “x” factor on this case. The court’s eight other members split, 4-4, last year on a case challenging the California Teachers Association on the issue of “fair share” fees, which left a lower court ruling in favor of those fees in place. Gorsuch represents the deciding ninth vote, having filled the vacant seat created by Justice Antonin Scalia’s 2016 death. And given his conservative credentials, most legal observers expect Gorsuch to join his fellow Republican-appointed colleagues in ruling against the unions.

Gorsuch, however, did not tip his hand Monday, watching silently as the other justices prodded and probed the attorneys arguing for each side. At times, Gorsuch rested his chin in his hands, looking quizzical; at others, he quietly scribbled notes. He did not once open his mouth, joining Justice Clarence Thomas (who almost never asks questions during oral arguments) as the only two justices who did not speak during the hourlong proceedings.

2. None of the other justices is wavering

Gorsuch’s eight colleagues all seemed virtually set in their opinions on the legality of the union fees.

Justices Sonia Sotomayor, who was nominated by President Barack Obama, and Stephen Breyer, nominated by Bill Clinton, were particularly outspoken in questioning the legal rationale behind Janus’ challenge, arguing there is lengthy precedent for allowing state and local governments to limit the behavior of public employees.

On the other side of the ledger, the four Republican-nominated judges were openly skeptical.

“Your argument doesn’t hold much weight,” Justice Anthony Kennedy told Illinois Solicitor General David Franklin at one point.

3. California is center stage

While Janus is suing the state of Illinois, California is the state that will feel the biggest impact from the court’s decision. Roughly 18 percent of the country’s 14.8 million union members reside in California. And the state has the most government employees of any in the nation.

It’s not surprising then, that California’s public sector unions are particularly strong and politically active, including those representing teachers, prison guards and law enforcement. They not only shape the debate on labor issues but also channel millions of dollars in support of favored ballot measures and politicians.

The state came up a couple of times during Monday’s arguments as the justices weighed the impact of overruling existing law on “fair share” fees. Several of the liberal justices worried about how disruptive it would be to strike down “fair share” fees. “Thousands of municipalities would have contracts invalidated,” noted Sotomayor. “Those contracts probably cover millions, maybe up to over 10 million, workers.” Breyer pointed out that the state of California filed its own friend-of-the-court brief in January that detailed concerns that such a decision would upend its “longstanding system of labor relations.”

An attorney for Janus dismissed those trepidations. “These contracts will expire the next one to three years and need to be renegotiated anyways,” William Messenger pointed out.

4. Political implications of the case are a factor in the arguments

In one of the most damaging exchanges for union defenders, Kennedy invoked unions’ own warnings about how the end of “fair share” fees would harm union power to undermine their argument.

“If you do not prevail in this case,” Kennedy asked AFSCME attorney David Frederick, “the unions will have less political influence; yes or no?”

Frederick conceded they would have less, even though the fees don’t go towards political causes.

“Isn’t that the end of this case?” Kennedy asked, rhetorically.

5. It’s not just union political power that’s at stake

Unions are a major force in the country’s partisan politics, bolstering Democratic candidates and liberal causes around the country. The lineup of speakers at a rally supporting unions and “fair share” fees outside the Supreme Court on Monday underscored how the case has galvanized a range of liberal groups, including civil rights and gay rights advocates. Collective bargaining agreements have helped prevent discrimination in the workplace, Mary Beth Maxwell of the Human Rights Campaign told the crowd gathered in front of the court after Monday’s argument.

A few hundred feet further down on the Court’s steps, conservatives staged their own rally in support of Janus and his lawsuit. The case is the pinnacle of a yearslong campaign by conservative groups to help propel legal challenges to public sector unions through the courts. According to leaked documents, one of the groups, the Bradley Foundation, made plain in a 2016 meeting that the cases against unions were part of a broader mission to challenge “the Left’s national agenda.”

The court’s ruling, expected in June, is likely to notch them a significant victory in that battle.

Emily Cadei is a writer with the McClatchy Washington Bureau.