Democrats led by Massachusetts Sen. Elizabeth Warren are trying to hobble President Trump's efforts to transform the National Labor Relations Board, the main federal labor law enforcement agency, into a pro-business institution.

The party has ensured that one newly confirmed board member, William Emanuel, may have to recuse himself from several major cases, preventing the NLRB from having a Republican majority in rulings. The labor board operates by a simple majority vote and is currently composed of three Republican appointees and two holdovers from former President Barack Obama’s administration.

In late November, a group of lawmakers led by Warren sought and obtained from Emanuel a list of hundreds of companies his firm did business with. He pledged he would recuse himself from any case involving those companies for "two years following my appointment to the NLRB.”

The list included such major companies as Amazon, Carmax, DirecTV, FedEx Freight, Hearst Corp., JPMorgan Chase, M&T Bank, Nissan North America, Rite Aid, Staples, Target, Time Inc., and Uber, among many others.

In the same letter, Emanuel recused himself from 98 cases currently before the board.

“Sen. Warren believes that due to recusal requirements, Mr. Emanuel will hinder the NLRB’s ability to function smoothly,” a staffer for the senator told the Washington Examiner.

In effect, the Democrats are putting Emanuel on notice that they will be ready to pounce should he not abide by his promise. “Sen. Warren will closely monitor future NLRB cases to ensure Mr. Emanuel recuses himself from decisions involving his former clients and parties represented by his former employer.”

A spokesman for the board who requested anonymity noted that the board would continue to decide cases as long as it has a quorum of at least three members. “The existence of four board members on particular cases does not prevent the board from deciding cases,” the source said.

The same source conceded, however, that “whenever cases are decided by four members, the possibility exists that the board will be evenly divided, and the resolution of these situations depends on the circumstances.”

Wilma Liebman, who served as board chairman during the Obama administration, said: "It is a large list. Perhaps not surprising for him — He’s had a long career, and Littler is a very large firm. Not that I’ve seen the lists supplied by other board members coming from big firms, but standing alone, it is a long list."

Business groups, none of whom would speak on the record about potential recusals, are hoping it doesn’t come to that, at least not often. Nevertheless, the situation might not be that bad for them since a deadlocked board won’t be able to do much. On the other hand, it may not be able to revisit moves that the board made under Obama, either.

Trey Kovacs, labor policy expert at the libertarian Competitive Enterprise Institute, argued that Warren was making a mountain out of a molehill. “In most instances, a panel of three board members decide cases before the NLRB. Usually, the full board only decides novel or potential precedent-changing cases,” Kovacs noted. “Unless all of Mr. Emanuel’s former clients are involved cases that are novel or precedent changing, which is unlikely, the NLRB will be able to operate just fine and simply assign other members to hear those cases.”

So, the recusals will matter only if one of Emanuel’s clients is involved in a “notable” case. That’s still a big "if," though.

Once a little-known agency, the NLRB gained a reputation for pro-labor activism under Obama. It sought to expand when businesses were legally liable for other businesses’ workforces, to speed up union workplace elections and to force businesses to turn over employee contact information to unions, among other changes.

The board made headlines by saying in 2012 that Boeing retaliated against its Washington state employees by opening a new factory in South Carolina even though no one was laid off. It is pursuing a precedent-setting case against McDonald’s Corp., arguing it is legally responsible for workplace violations by its franchises.

President Trump has sought to steadily reverse that pro-labor stance, appointing people to the board who have drawn cheers from business groups and Republican lawmakers, who argue the board should be a purely neural arbiter of cases.

In January, Trump appointed Philip Miscimarra, then the board's then-lone Republican member, as chairman. The Senate in August approved former GOP House staffer Marvin Kaplan to an open seat on the board. The following month it approved Emanuel, a former private attorney with the management-side firm Littler Mendelson, to another open seat. The Senate also confirmed private-sector lawyer Peter Robb to be the board's general counsel last month, replacing Richard Griffin, an Obama appointee noted for his activist stance.

That briefly gave the board a 3-2 Republican majority. The Trump White House soon will have to appoint yet another member to the board because Miscimarra officially steps down Dec. 16.

Trump has not nominated a replacement for him, although business lawyer John Ring was widely rumored by trade groups to be the administration’s top candidate. A spokesman for the White House said they had no personnel announcements to make.