Washington, D.C., will have a Democratic Socialist mayor after November’s election, and Congress is moving to obstruct her before she takes office.

The House oversight committee last week advanced legislation to block the most popular of the tax reforms under debate in the district.

Janeese Lewis George, a Zohran Mamdani on the Potomac — a rising progressive champion who shares his dedication to working families — is all but certain to win November’s mayoral election after her Democratic primary victory last month. She wants a new “business activity tax” targeting lobbying shops, law firms, and other businesses that profit from D.C.’s location while their owners live in the suburbs and pay taxes elsewhere — which is a lot of them. Ms. Lewis George says the measure could raise $500 million in new revenue to fund schools, housing, and public transit her constituents desperately need. The threat that firms will flee is the same bluff corporations trot out whenever they are asked to pay their fair share, and it rarely materializes.

Enter Congressional Republicans, acting as the absentee landlords of the federal district. Congress exercises control under the U.S. Constitution, although since the 1970s federal lawmakers have wisely given city politicians wide latitude via “home rule.” Home rule is only as strong as Congress’s willingness to respect it, and this week the House made its willingness plain: the committee on Wednesday approved a bill requiring an explicit Congressional sign-off for all tax measures, putting the district’s budget under the veto of representatives whose constituents do not vote in D.C.

Ms. Lewis George’s business tax is one target; a sensible tax on investment income under debate in the City Council is another.

The House bill is an affront to self-government — it would strip the district’s elected representatives of the power to set their own tax policy, handing that power to a Congress whose members were not elected by D.C. residents. It is written in a broad way that could entangle Congress in every aspect of city governance, which is probably exactly what its authors intend.

But the message to district politicians is clear: Federal lawmakers are worried about a pro-worker tilt in the city. They claim to care because all Americans have a stake in a federal district that is safe, prosperous, and pleasant to visit. What they really mean is that lobbyists and law-firm partners should not have to pay for the city they use.

The question for the Democratic Socialist project is how to govern when a hostile Congress blocks every attempt to make the wealthy contribute their share. The mayor will face tough governing decisions. But the bigger question is whether a Congress that refuses to let D.C. raise its own taxes is fit to govern anything at all.