Washington — A key surveillance tool that lets the government collect foreign intelligence without a warrant is again at the brink of expiration. Barring an 11th-hour intervention, the spy authority, known as Section 702 of the Foreign Intelligence Surveillance Act, is set to lapse at 12 a.m. Saturday after President Trump's pick to oversee the nation's intelligence agencies complicated its renewal.Democrats have opposed extending the authority since the president announced that he had selected Bill Pulte, the head of the Federal Housing Finance Agency, to temporarily serve as director of national intelligence. In addition to his lack of national security experience, Democrats railed against Pulte for his efforts to go after some of Mr. Trump's political foes on allegations of mortgage fraud. Lawmakers have long sounded the alarm about the risks of letting Section 702 expire. Those who serve on congressional intelligence committees say that about 60% of the president's daily intelligence briefing is derived from information collected under the law, and they consider it a tool that is critically important to national security. But it's still controversial: the provision already faced stiff opposition from civil liberties-minded lawmakers in both parties who have unsuccessfully pushed for years to implement a requirement for a warrant to search Americans' data that's incidentally swept up in the collection. Demands for reforms led Congress to punt the issue twice since its initial expiration in April. Here's what to know about what happens next.What does Section 702 do? Section 702 was first authorized in 2008 and allows the government to sweep up the electronic communications of foreigners abroad without a warrant. Senate Majority Leader John Thune has noted that policymakers across the federal government rely on the information it provides on a regular basis.