Organized labor and its allies in the Democratic Party are bracing for a major hit to union power now that Justice Neil Gorsuch has a seat on the Supreme Court, fearing that he will tip the balance of the court toward overturning key legal precedents that benefit labor.

"This justice is poised to cast the fifth vote to make it next to impossible for public-sector labor unions to organize," said Tom Perez, chairman of the Democratic National Committee and former secretary of labor, in a speech Tuesday to the United Steelworkers union.

The two main cases on the court's horizon that unions are worried about are Yohn v. California Teachers Association and Janus v. AFSCME. Both could overturn a 1979 precedent called Abood that said public-sector workers could be forced to join a union or support one financially as a condition of employment.

Such requirements — called "security clauses" in union parlance — are a common feature of public-sector union contracts. They are a key source of the unions' strength since they boost both membership and dues revenue.

Terry Pell, executive director of the Center for Individual Rights, a legal nonprofit representing the plaintiffs in Yohn, believes they have a good chance of reaching the Supreme Court later this year.

"We are arguing that we are raising concerns that can only be answered by the Supreme Court," Pell told the Washington Examiner. They did it once before in a case the Supreme Court heard last year called Friedrichs v. California Teachers Association.

Friedrichs' argued that the state's security clause violated the teachers' rights because it forced them to subsidize the union's political activities even when they disagree with the labor group's agenda.

A majority of the justices appeared to be on the verge of overturning Abood, but Justice Antonin Scalia's death just one month after oral arguments meant that they deadlocked 4-4. That meant that the lower court opinion upholding Abood stood.

"But for the death of Justice Scalia that case would already be decided," Perez said.

Because the Supreme Court technically never reached a judgment on the issue, nothing prevents it from taking up the same question again.

"We are currently before the same district court judge we were in the Friedrichs case," Pell said. The issue at question in Yohn is basically the same as in the prior case, so Pell expects a similar ruling that will enable the case to reach Supreme Court.

The Janus v. AFSCME case, which has been in the 7th Court of Appeals, raises similar issues. The National Right to Work Foundation and the Liberty Justice Center, two free-market nonprofit groups, filed the case on behalf of two Illinois health department employees.

"We're at the point now where the next step is to file for cert with the Supreme Court," said foundation spokesman Pat Semmens, referring to the procedure for asking the justices to take up their case.

Unions who believe they caught a break when the court split on Friedrichs are eyeing both cases nervously. They were cited in a resolution passed by NYSUT, a 6000,000-member federation of New York teachers and school employees, after Gorsuch was confirmed April 10.

The resolution warned that the cases could tip the court toward "invalidat[ing] of the collection of fair share fees by public-sector unions." That would "deliver a crippling blow to the labor movement and to public-sector unions in particular."

A spokesman for the Service Employees International Union told the Washington Post Friday that the union had trimmed its budget by as much as 30 percent this year in expectation that it soon will face a much tougher organizing climate.

"These particular budget cuts are our way of enacting financial efficiencies to deal with the realities posed by extremist right-wing labor policy in all branches of the federal government," Sahar Wali told the Post.

SEIU in particular has reason to be worried, as it has a suffered series of defeats at the court in recent years.

In 2014's Harris v. Quinn, the court ruled 5-4 that state-funded Illinois home healthcare workers were not state employees eligible for unionization. That was a blow to the SEIU, which represented them.

In 2012's Knox v. SEIU, a 7-2 majority ruled that the union could not force members to pay a special assessment fee the union imposed on the workers without giving them the opportunity to opt out first. SEIU had made the assessment to raise funds to defeat state ballot initiatives it opposed.

Pell cautioned that it is not clear how Gorsuch, though a conservative, would vote on labor issues since he has little record on the subject. "It's never a good idea to take any [Supreme Court] vote for granted."

Semmens echoed that assessment, saying, "The only thing we know for certain is that he will be the deciding vote."