It’s sad, really. The beleaguered labor unions of America thought that they had finally found a true friend. In Joe Biden, they had a man who was the most pro-union president in my lifetime – a low bar to clear, but something. Yet this week we found out that when the fight got hard, Biden had the same thing to say to working people that his Democratic predecessors have for decades: “You’ll never get anything you want if I don’t win; but once I win, I can’t do the things you need, because then I wouldn’t be able to win again.”

At the same time that thousands of union members are fanned out across the state of Georgia knocking on doors to get Raphael Warnock elected and solidify Democratic control of the Senate – to save the working class, of course! – Biden decided to sell out workers in the single biggest labor battle of his administration. Rather than allowing the nation’s railroad workers to exercise their right to strike, he used his power to intervene and force them to accept a deal that a majority of those workers found to be unacceptable.

His ability to do this rests on the vagaries of the Railway Labor Act, but all you really need to understand is this: nobody forced him to side with the railroad companies over the workers. That was a choice. The White House just weighed the political damage it anticipated from Republicans screaming about a Christmas-season rail strike against the fact that railroad workers have inhuman working conditions and would need to go on strike to change that, and chose the easier political route. This was a “Which side are you on?” moment, and Biden made his position clear.

What were these railroad workers fighting for? Paid sick leave. The basic ability to call in sick or go see a doctor without being penalized, something that many of us – including members of Congress and railroad company executives – take for granted. It is also, by the way, a right that Joe Biden believes should be codified into federal law. But he must not believe in it all that much, since he just cut the legs out from under unions who were trying to secure it for their members.

And why is it so difficult for railroad workers to win this basic right? Their industry, after all, is fantastically profitable. It has cut its workforce to the bone purely to enrich investors, and doesn’t want to spend the money it would take to staff properly so that its remaining workers could take sick days. Greed, and nothing more. The combined power of the railway unions could overcome this obstacle, but only if they have the ability to go on strike. Railroad companies are not stupid. They knew the White House would intervene to prevent a strike, so they felt no urgency to give in to their workers’ demands. Joe Biden, Mr I-Love-Unions, unilaterally disarmed the unions before their fight could begin. Without a credible strike threat, they never had a chance.

People will point out that strikes are disruptive. Yes. That’s the point. A rail strike would be so disruptive that the rail companies probably would have given up the sick days to prevent it – and if they didn’t, the White House could have weighed in on the side of the workers to make them. Instead, it did the opposite, and rescuing hope for those workers fell to Bernie Sanders and to progressives in the House, who forced congressional leaders to move a separate bill to guarantee the sick leave they were asking for. As usual, it was the left that went to the trouble of fighting for labor after the party’s mainstream sold it out for the sake of convenience.

Organized labor is in an abusive relationship with the Democratic party. For decades, Democratic administrations have failed to prioritize labor issues and stabbed unions in the back, and the union establishment has always showed up with a big check for them in the next election. I guarantee you that this will happen again after this betrayal by Joe Biden. (You may have already noticed that few union leaders have been brave enough to criticize the White House directly on this issue.)

Breaking free from this dynamic does not mean getting friendly with the Republicans, who would happily bring back indentured servants and child labor if they could. It means going left, to the only part of the political spectrum that genuinely gives a damn about the interests of working people. Rather than pouring its considerable resources into the mainstream Democrats, the labor movement should be bankrolling the expansion of the progressive wing of the party, to permanently shift the internal balance of power. This is not some rarefied ideological prescription from a textbook; it is common sense. If you are a railroad worker – or anyone who understands the basic need for solidarity among all workers in the face of corporate power – where are your friends? They are all sitting on the left. If we keep running back to support those who just kicked sand in our faces, nothing will ever change.

And instead of kissing and making up with Biden after this outrageous insult, labor should be putting the fear of God in him with the possibility that they will back a primary presidential challenge from the left in 2024. Biden is very old and not very popular. He has been a friend to unions, yes, but if he goes against them on the biggest fight of all, how much of a friend is he, really?

Nothing has as much latent power as organized working people. We need to stop begging politicians for their support, and make them come beg for ours. Just because a strike is illegal, after all, doesn’t mean that it can’t happen.

• Hamilton Nolan is a writer at In These Times