With all 49 Republicans already in favor and many Democrats still undecided, Biden’s party is highly alarmed that the disapproval resolution could pass. That outcome would spotlight the party’s divide over the issues of crime and D.C. self-governance.

“I have concerns about passage here. Of course, the president could veto. He’s going to have to make that decision,” said Sen. Chris Van Hollen (D-Md.). “Congress shouldn’t be bigfooting decisions made by the elected representatives of the people of the District. I will be talking with [Democrats] about this general principle.”

Biden has come out in opposition to the legislation but not made an explicit veto threat. Democratic leaders believe he is prepared to do so: “I’d assume, but I wouldn’t go any further,” said Senate Majority Whip Dick Durbin (D-Ill.), who chairs the Judiciary Committee.

The reversal of D.C.‘s crime law cannot be filibustered, and if 51 senators vote yes it would be the first time since 1991 that Congress has rolled back a statute in the capital city. It’s a stunning turnaround from last Congress, when 46 senators in the Democratic Caucus went on record to support making D.C. a state while the Democratic House passed its own statehood bill.

And the shift is in part thanks to the stubborn crime problem in the city members call their part-time home: Rep. Angie Craig (D-Minn.), who was assaulted in her apartment building last week, was among the Democrats who supported rolling back the D.C. Council’s plan to make changes to some criminal penalties and scrap some mandatory minimum sentences.

It would only take two Senate defections for the measure to head to Biden’s desk, and Republicans feel they are on the cusp of getting them. In an interview, Sen. Joe Manchin (D-W.Va.) indicated interest in the proposal, though he has not made a firm decision.

“In West Virginia, they want the tougher codes,” he said. “I would be open to seeing what they want to roll back, and make sure it’s common sense. If it’s reasonable and common sense, yeah.”

Democrats can more easily block a second House-passed resolution that looked to stop a new city voting rights law that allows noncitizens to vote in local elections. That resolution is not eligible for expedited floor proceedings, and Democrats can bottle it up in committee and object to bringing it up on the floor, according to two people familiar with the floor schedule.

The crime proposal won’t come to the floor for several weeks. When it does, it may be one of the first tough votes this Congress for Senate Democrats — who control the Senate but cannot stop the disapproval resolution.

Several Democrats said they were not ready to comment on the crime proposal, including Sens. Jon Tester (D-Mont.), Catherine Cortez Masto (D-Nev.), Michael Bennet (D-Colo.), Sherrod Brown (D-Ohio), Angus King (I-Maine) and Mark Kelly (D-Ariz.). Manchin, Kelly, King and Sen. Kyrsten Sinema (I-Ariz.) did not co-sponsor a bill to grant D.C. statehood last Congress.

Some other Democrats said that, philosophically, Congress should not be chipping away at the city’s autonomy. Washington residents pay taxes but lack congressional representation and are subject to the legislative branch’s oversight on a plethora of matters. The last time Congress rolled back a D.C. law, it was to stop a building from exceeding height limits.

Since that 1991 episode, Congress has attached riders to larger pieces of legislation to block implementation of the city’s marijuana laws and restrict abortion funding, but this is the first time in a generation that the House and Senate may actively roll back policy passed by the city council. As an undecided Sen. Tina Smith (D-Minn.) put it: “I’m generally not in favor of undoing things that a local government has done.”

“I don’t think Congress should be, you know, in the role of making them play Mother-May-I on everything,” said Sen. Tim Kaine (D-Va.), a former mayor and governor. “My default on these is: I’m pretty strongly a home rule guy. When it gets closer we’ll take a look.”

Senate Republicans took a first step this week, with Sen. Bill Hagerty (R-Tenn.) introducing his resolution of disapproval. In a statement to POLITICO, Sen. Rand Paul (R-Ky.) said he will support the bill, sealing the 49th and final GOP vote and shifting the focus to Democrats.

“While I have always been supportive of ending mandatory minimums for nonviolent crimes, I do not think mandatory minimums should be lifted for violent crimes. Because the D.C. bill reduces sentences for violent crime I will support efforts to overturn the D.C. law,” Paul said.

Even if the resolution gets to 51 votes, it won’t be the end of the story. Biden still has his veto pen.

“My hope is the president would veto it and stand with the residents of the District of Columbia, stand on principle and recognize that this is not a soft-on-crime piece of legislation,” D.C. Attorney General Brian Schwalb said in an interview.

If Biden vetoes the effort, Congress has a high bar to overcome it: two-thirds of both the House and Senate. That would mean at least 17 Senate Democrats and 290 total House members. Thirty-one House Democrats supported the measure, putting it well short of that threshold.

The White House said in a statement of administration policy that it opposes the resolution and that “Congress should respect the District of Columbia’s autonomy to govern its own local affairs.” Should he go further and explicitly vow to veto the disapproval resolution, it could affect those Democrats who are on the fence.

“Anytime the president says that he will veto something, it changes the calculus,” said Sen. Richard Blumenthal (D-Conn.). “It means that members may be a lot less inclined to take a position contrary to the president when they know his opposition is so clear.”

Were the measure to clear Biden’s desk, it would send a signal to the House GOP that it could continue to roll back District laws the conference didn’t agree with. And even if Biden successfully vetoes the resolution, it’s clear that House Republicans are more than willing to battle the D.C. government over its ability to govern itself.

It’s a sobering reminder for statehood advocates that the window to seek more autonomy has passed — and it’s not clear when it will come again.

“A couple of years ago, it looked like we were on the doorstep of becoming the 51st state. We still have to work hard every day to aspire to that,” Schwalb said. “We’re now at the whims and the vagaries of a certain small group of politicians who are using the District of Columbia as a prop.”