Before he took office, President Joe Biden vowed to be “the most pro-union president you’ve ever seen.”

Just hours after being sworn in, he fired Peter Robb, general counsel of the National Labor Relations Board, who previously worked for union-busting law firms and the Reagan administration during the Professional Air Traffic Controllers Organization (PATCO) strike. Biden subsequently issued executive orders guaranteeing collective bargaining rights and a $15-per-hour minimum wage for federal employees and government contract workers. And on Sunday, in his most surprising pro-union action yet, Biden released a video referencing the Amazon organizing drive in Alabama, warning employers not to retaliate against workers.

“There should be no intimidation, no coercion, no threats, no anti-union propaganda,” Biden said. “No supervisor should confront employees about their union preferences. You know, every worker should have a free and fair choice to join a union. The law guarantees that choice.”

After decades of anti-union presidents — or presidents who say one thing about worker power and do the exact opposite — Joe Biden could easily coast along on Sunday’s video. It was arguably the most pro-union statement a US president has made in decades. It was a welcome departure from previous presidential inaction (even if it will have to be backed up by an NLRB vigorously enforcing workers’ rights).

But here’s the real litmus test for Biden: the Protecting the Right to Organize (PRO) Act.

If Biden wants to be regarded as the most pro-union president we’ve ever seen, he will have to use his political capital to change the rules of the game for US workers, who face one of the most hostile organizing environments in the entire world.

The PRO Act is the most sweeping pro-labor legislation in decades. It would effectively end anti-union “right-to-work” laws (currently on the books in twenty-eight states), institute financial penalties on employers that retaliate against workers who organize, prohibit employers’ “captive audience” meetings, require employers to bargain a first contract in good faith, repeal the prohibition on secondary boycotts (an instrument of worker solidarity banned since the late 1940s), and bar employers from permanently replacing strikers.

In one fell swoop, the PRO Act would transform the organizing terrain for workers. It would make it far easier for workers to form unions, without employer interference, and for workers to use their collective power to advance their interests. It would be a game-changer in the United States — and that’s why the business community has already come out swinging against it. The US Chamber of Commerce warns that it would “fundamentally alter our nation’s system of labor relations.”

The last time labor legislation was on the agenda was in the Obama years with the Employee Free Choice Act (EFCA), also known as card check. Although the bill was more limited in scope than the PRO Act, business PACs outspent unions five to one lobbying to defeat the EFCA during the 2007–8 election cycle. The US Chamber of Commerce alone shelled out more than $400,000 for every day that Congress was in session. Barack Obama, like Biden, campaigned on promising to pass the EFCA. But it died in the Senate, with minimal support from the Obama administration.

Biden’s campaign materials not only indicate his support for the PRO Act, but promise to “go beyond” it. Yet he’s been all but silent on the PRO Act since he’s taken office. Last month, the PRO Act passed the House — but now it’s in the Senate, where it is likely to meet the same fate as the EFCA if the Biden administration doesn’t intervene.

Biden is the most powerful politician in the world, and he must lead publicly on the importance of the PRO Act — not just say the right things to unions behind closed doors. Vice President Kamala Harris also has a role to play; she is the tiebreaker and leads the Senate, and could override the parliamentarian to get the PRO Act passed by reconciliation. Or Biden could just use his bully pulpit to say that he wants the bill passed no matter what and that the Senate should end the filibuster to do it.

It’s entirely up to Biden how hard he wants to push this. But if he wants to be seen as “Joe from Scranton,” or known as the “most pro-union President [we’ve] ever seen,” he’ll need to build on his statement on Sunday. He’ll need to actually fight to pass the PRO Act.