WASHINGTON — Justice Neil Gorsuch will be the deciding vote in a blockbuster Supreme Court case pitting powerful public-sector labor unions against well-funded conservative groups.

The Trump appointee remained silent during yesterday’s oral arguments in the case, declining to tip his hand in a case that previously deadlocked his colleagues, 4-4, before he joined the bench. But Democrats expect his vote will deal a major political blow to the strength of public-sector unions ahead of this year’s midterm elections.

The case considers the constitutionality of requiring “agency fees” be paid to public-sector unions by nonunion members. Unions argue that their collective bargaining efforts benefit all workers, and the fees solve the free-rider problem and aren’t used for political activities. But challengers claim the fees amount to forced political speech, violating their First Amendment rights.

The case is one of many legal challenges against public-sector labor unions — still a major force in favor of Democrats — funded at least in part by conservative groups and donors including Charles and David Koch. Democrats fear that the court’s likely ruling with be a blow to the kneecaps for the party’s efforts to reclaim congressional control in this year’s elections, and the White House in 2020.

While high court justices are meant to be above the political fray, U.S. Sen. Elizabeth Warren said Gorsuch has shown himself to be a political player. The day the court agreed to take up the union fee case, Warren said, Gorsuch was “speaking at a luncheon at the Trump Hotel in Washington, D.C. — a luncheon funded by Charles Koch and by the Bradley Foundation.”

“These are two openly, openly anti-union groups,” Warren said yesterday at an AFL-CIO rally in Boston. “This was a blatant conflict of interest and he was so arrogant he didn’t care. He went out and was not only present at the luncheon, and he was the keynote speaker at the luncheon.”

The political impact of the case was not lost on the justices who did speak during yesterday’s arguments.

“If you do not prevail in this case, the unions will have less political influence — yes or no?” Justice Anthony Kennedy asked David Frederick, an attorney arguing on behalf of AFSCME.

“Yes, they will have less political influence,” Frederick said.

“Isn’t that the end of this case?” Kennedy said, suggesting that preserving public unions’ political clout isn’t a constitutionally justified reason for charging nonunion members.

Others noted the personal impact of a ruling invalidating laws requiring agency fees.

“Thousands of municipalities would have their contracts invalidated, (affecting) the livelihoods of millions of individuals all at once,” Justice Elena Kagan said. “When have we ever done something like that?”

Meghan Ottolini contributed to this report from Boston.

Minding the fees

By JORDAN FRIAS

Opinion was mixed yesterday on whether the Supreme Court should allow public unions to require?nonmembers pay dues.