Barring any last-minute compromises, powerful government surveillance authorities under the Patriot Act will expire at the stroke of midnight Monday. And they may never return.

This week, senators have been negotiating over whether to pass a House bill that would renew and tweak existing provisions in the long-controversial law, rather than let them “sunset” on June 1. But if the sunset comes and the provisions are off the books, lawmakers in both chambers would be facing a vote to reinstate controversial surveillance authorities, which is an entirely different political calculation.

Lawmakers may be unwilling to vote affirmatively for surveillance powers that many of them already dislike and have tried to rein in. “I think it is a real risk that if the provisions do expire, they would be more difficult to reinstate than to reform,” Representative Adam Schiff, the senior Democrat on the House Intelligence Committee, told The Daily Beast.

Schiff supports the USA Freedom Act, which overwhelmingly passed the House but failed to muster enough votes in a midnight Senate session last Saturday. The bill would end the NSA’s collection of phone records in bulk, but leave intact other surveillance tools that, while not broadly popular, are less controversial.

Schiff said it was easier to get lawmakers to support the Freedom Act with its changes to existing law than it would be to vote to re-enact law that had gone away.

Senator Mike Lee, who also supports the Freedom Act, shared that sentiment. “There were members who voted for the USA Freedom Act who would feel differently about reinstating those provisions” once they’ve lapsed, Lee told The Daily Beast. Lee said he was talking to colleagues this week to try to persuade them to support the bill before the clock runs out.

The political stakes for Congress are high, and novel. Asking members to reinstate the provisions would be akin to asking them to cast a new vote in favor of the Patriot Act, and that’s something that two-thirds of House members have never done in their legislative careers, said Harley Geiger, the advocacy director and senior counsel at the Center for Democracy & Technology. “If the provisions sunset, we enter uncharted waters, and I don’t really know what happens,” Geiger told The Daily Beast.

While lawmakers could once be counted on to reliably reauthorize the Patriot Act—and accuse opponents of risking national security if they failed to do so—leaks by Edward Snowden about spying operations have eroded the law’s support. In the House, USA Freedom was pitched as a compromise that would suspend the phone records program while leaving intact other measures that intelligence agencies say they need. The bill has enjoyed support among some privacy and civil liberties advocates.

The Senate will return on Sunday to make one last try to pass it. But if they fail, there’s no obvious way forward in either chamber. “The only way out of this box,” Schiff said, was for the Senate to pass the House bill.

Three major Patriot provisions are on the chopping block: so-called roving wiretaps, which let the government monitor one person’s multiple electronic devices; the “lone-wolf” provision, which allows surveillance of someone who’s not connected to a known terrorist group; and Section 215, which, among other things, the government uses to collect the records of all landline phone calls in the United States.

House lawmakers say they’re in no mood to bail the Senate out if it once again can’t muster the votes needed to head off a possible filibuster by surveillance opponents, most notably Senator Rand Paul and his allies, including Ted Cruz. Both men are running for president.

Schiff said the Freedom Act narrowly failed to pass—by three votes—in large part because Senate Majority Leader Mitch McConnell whipped senators not to support it. If the surveillance authorities expire, McConnell will bear the blame, Schiff said.

“This is something that ought to give McConnell great pause. I think he’s playing with fire here.”

The top members of the House Judiciary Committee have also warned their colleagues in the other chamber. “If the Senate chooses to allow these authorities to expire, they should do so knowing that sunset may be permanent,” Representatives Bob Goodlatte of Virginia and John Conyers of Michigan, the chair and ranking member of the Judiciary Committee, warned in a statement last week.

Lee remained optimistic that enough senators who initially voted “no” might switch their position when they return on Sunday and face the prospect of losing the surveillance authorities entirely. “Before the vote, some members told me that they would be willing to vote for USA Freedom,” Lee said. But he couldn’t say whether those members who’d been on the fence had come over to his position yet.

And, Lee cautioned, if the Senate fails to act and the provisions expire, he sees little opportunity to revive them with yet another bill. “I’ve thought a lot about this and it’s very difficult to see a political solution,” Lee said, noting that there were obviously not enough votes to reauthorize the Patriot Act as its stand now and leave the phone records program intact.

So what happens if, come Monday, the guts of the Patriot Act have been ripped out? In the short term, maybe not much.

The National Security Agency has already been shuttering the phone records program, which, intelligence officials acknowledge, isn’t all that useful in the first place. Investigations that are using phone records and that have already begun would probably be allowed to continue, legal experts said. And the government might be able to use other legal authorities, such as subpoenas, to obtain those records for a new investigation.

As for the roving wiretap provision, two former intelligence officials said that while it might fill gaps in the government’s ability to monitor potential threats, it’s far from the only tool in the kit. The government could probably use other surveillance laws to monitor a target’s multiple devices, they said.

The tool also hasn’t been used that often. In March 2011, Todd Hinnen, a senior national security official at the Justice Department, testified that roving wiretaps had been employed in a “small but steady number of national security investigations each year.” According to data from U.S. courts, in 2013, the most recent year for which figures are available, 11 federal wiretaps were designated as roving.

And the lone-wolf provision? It has never been used, senior administration officials told reporters in a briefing Wednesday.

Still, President Obama, FBI Director James Comey, and Attorney General Loretta Lynch have all described Section 215, roving wiretaps, and lone wolf as important authorities. Section 215 in particular, which authorized the phone records program, also allows the government to collect other kinds of records and is an important investigative aid, officials say.

An FBI spokesman told The Daily Beast that while the bureau has not yet used the lone-wolf provision, “it remains a very important tool to have in our toolbox, and one we wish to keep.” The provision, while contained in the Patriot Act, authorizes surveillance under a different statute, known as the Foreign Intelligence Surveillance Act, or FISA. And to date, the FBI has been able to establish probable cause to show that every individual who was monitored under FISA was acting on behalf of a terrorist group, the spokesman said.

But the bureau is concerned that there may come a time when they can’t do that, he added. “In that situation, we would need to rely upon the Lone Wolf provision in order to gather foreign intelligence under FISA and keep the American public safe.”

In the briefing with reporters, a senior administration official warned that Congress was playing “Russian roulette” with U.S. national security by not passing the Freedom Act. And during a briefing on corruption charges brought against the FIFA soccer organization, Lynch said that if the provisions expire, it will create “a serious lapse in our ability to protect the American people.”

But notably, the administration has waited until now, just as the authorities are about to expire, to mount this coordinated effort to pressure Congress. And it pales in comparison to previous attempts to preserve surveillance programs.

In 2007, the George W. Bush administration dispatched its most senior national security officials to brief Congress and the press on multiple occasions about changes to the Foreign Intelligence Surveillance Act, warning that if lawmakers didn’t act, the nation would be at grave risk of a terrorist attack.

Obama, by contrast, has mostly taken a cooler approach, urging Congress to pass the Freedom Act, but not warning that the sky will fall if they don’t. That may reflect a calculation on the president’s part that the surveillance authorities aren’t important enough to lose political capital fighting to keep them.

Looking ahead to Sunday’s Senate session, Schiff said, “I don’t feel confident at all” that lawmakers will pass the Freedom Act.

And that may suit civil libertarians and privacy advocates just fine.

Geiger, with the Center for Democracy and Technology, said, “We hope that if the Senate fails to pass meaningful surveillance reform that it does lead to a sunset, and then meaningful reform of the Patriot Act.”