The Senate on Wednesday approved President Trump's pick of Marvin Kaplan to fill an open seat on the National Labor Relations Board, the main federal labor law enforcement agency.

The 50-48 vote came after the Republican majority broke a Democratic filibuster on the nomination earlier in the day by another 50-48 vote.

Democrats and organized labor groups opposed the pick. Sen. Elizabeth Warren, D-Mass., called the NLRB "the most important federal agency you've never heard of" since it enforces the National Labor Relations Act, the law that protects the right to unionize. "As a Republican House staffer, he actively worked to strip workers of their rights," Warren said.

Prior to his confirmation, Kaplan was chief counsel of the Occupational Safety and Health Review Commission. Until 2015, he was as a Republican staffer for the House Education and the Workforce Committee, where he assisted Republicans heavily critical of the NLRB's actions under former President Barack Obama.

Supporters of the pick argue that the board tilted heavily pro-union under Obama and that Kaplan's confirmation would restore balance. "The confirmation of Marvin Kaplan to the National Labor Relations Board will get the agency one step closer to being able to take up desperately needed reforms. In recent years, the NLRB has put out job-killing decisions and regulations that favor the interests of organized labor over individual workers and job creators," said Trey Kovacs, labor policy expert with the free-market Competitive Enterprise Institute think tank.

With Trump's choice for the NLRB's other open seat, William Emanuel, Kaplan would give the board a Republican-led majority for the first time since President George W. Bush.