Just as we warned in Monday’s Post, poor Sen. Bernie Sanders is now the target of formal labor grievances even though he’s bowed to union demands for higher pay and better benefits.

Specifically, the anonymous complaint filed with the National Labor Relations Board alleges that the senator’s Iowa presidential-campaign office fired at least three staffers for their involvement in organizing and labor activities.

It also claims the campaign failed to inform workers of their rights under the collective-bargaining agreement with the union and to provide comp days off after making staff work extra time.

Don’t be too fast to call Bernie a hypocrite here: False accusations are a regular feature of labor relations, especially in unionized shops.

That said, Sanders has already flirted with labor-law violations by publicly fuming about workers going to the press over his other dispute (over claims that he’d failed to pay the contractual $15 wage) with United Food Commercial Workers Local 400.

The irony is that, after a lifetime talking up the virtues of a unionized workplace, it’s only now that Sanders is learning about the problems that go with it.

Hmm: Maybe every Democratic campaign should have to be a union shop.