WASHINGTON, DC - NOVEMBER 13: U.S. Sen. Bernie Sanders (ID-VT) speaks during a Conference on the FY2014 Budget Resolution meeting November 13, 2013 on Capitol Hill in Washington, DC. Congressional Budget Office Director Doug Elmendorf briefed the conferees on CBO's budget and economic outlook. (Photo by Alex Wong/Getty Images)

U.S. Sen. Bernie Sanders (I-Vt.) asked on Friday whether the National Security Agency has trained its surveillance apparatus on members of Congress.

“Has the NSA spied, or is the NSA currently spying, on members of Congress or other American elected officials?” Sanders asked in a letter to NSA chief Gen. Keith Alexander.

Under Sanders' definition, "spying" would include gathering metadata from official or personal phones, or “'any other data from a third party not made available to the general public in the regular course of business."

Sanders has repeatedly voted against the Patriot Act, the legislation that authorizes the NSA's collection of phone metadata, and in June introduced a bill to end bulk collection.

The NSA, for its part, has rejected the suggestion that the collection of metadata on American phone calls and emails really counts as "spying." The agency did not immediately respond to a request for comment on Sanders' letter.

Yet, it was not long ago that the agency spied on members of Congress: In the 1980s, the NSA intercepted calls between Maryland Rep. Michael D. Barnes (D) and government officials in Nicaragua. Transcripts wound up in the hands of officials in President Ronald Reagan's administration.

Today, the ACLU has expressed concern about the prospect of NSA blackmail against antagonistic members of Congress, and Sen. Carl Levin (D-Mich.) has publicly shuddered at the thought of the technology in the hands of former FBI Director J. Edgar Hoover.

Other members of Congress are not so worried. Sen. Dianne Feinstein (D-Calif.), who chairs the Senate Intelligence Committee, has steadfastly defended the NSA call-monitoring program.

"This is not a surveillance program," Feinstein wrote in a November op-ed. "In the case of the call-records program, neither individuals nor their phone conversations are being listened to. No one is being monitored. And no one is being watched under the call-record program."

UPDATE: 1/4: NSA spokesperson Vanee' Vines responded to Sanders' letter on Saturday in an emailed statement: