In lieu of a straight Section 215 reauthorization, Congress is likely to pass some version of the USA Freedom Act, which would replace bulk data collection with a system under which the NSA must request call records from the telecom companies that hold them. The act would also eliminate national security letters, which the FBI can use to gather private data on consumers in secret and without court approval.

Surveillance that was launched under the now-defunct passages can even continue, thanks to a grandfather clause in the Patriot Act, which allows the federal government to proceed with its spying if it was authorized under expired provisions.

American University Washington College of Law professor Stephen Vladeck said the government could argue that the grandfather clause goes even further than that.

“The government might also argue they could get a new authorization as long as the investigation was ongoing,” said Vladeck. And because investigations can be broadly defined, “the government could at least try to backdoor through the grandfather clause most of what the front door now precludes.”

But Vladeck described the grandfather clause as “a bit of a red herring,” given the likely passage of the USA Freedom Act.

“If it didn't look like the Senate was going to pass USA Freedom in the next three days, I think it would be more of a big deal,” he said.

The ACLU has declined to support or oppose the USA Freedom Act, calling it an improvement on the Patriot Act but still dangerously broad in the power it allocates to the NSA.

“It’s not as bad as saying to the phone companies, ‘Give me everything and everyone,’ but it is sufficiently broad for them to collect hundreds of records at a time,” said Singh Guliani.

Whether the USA Freedom Act will reach the president’s desk in its present form remains to be seen. Senate Majority Leader Mitch McConnell, R-Ky., who initially supported a straight extension of the Patriot Act language, has proposed several amendments to the House version of the bill. The ACLU is urging changes of its own to narrow the scope of the law.

Whichever side wins the push and pull over the USA Freedom Act, the passage of that legislation will not end the political struggle over NSA spying. Mass surveillance will likely continue, as will the fight over its scope. The death of Section 215 brings to a close just one act in a much longer drama.