Sen. Mark Udall (D-CO) was one of just a few US Senators decrying widespread surveillance even before the Snowden leaks. Udall has been a sharp critic of intelligence agencies since then as well, asking for CIA Director John Brennan to resign after allegations emerged that the intelligence agency gained access to Senate files.

He won't be in office much longer. Udall lost his election last night against Republican challenger Rep. Cory Gardner. By 1:00am Eastern time, Gardner was ahead by six percentage points, with 87 percent of precincts reporting. At that point, several news agencies called the election for Gardner. The Senate seat was one of several that flipped from Democratic to Republican control last night, causing Republicans to take control of the upper house.

Udall's positioning as a tough critic of the NSA wasn't a big issue on the campaign trail, although in the final days of the election he did release an ad saying he “won’t tolerate” overbroad government surveillance. But much of Udall's campaigning came across as out of touch, running an old playbook. Udall hammered his opponent on womens' issues in socially liberal Colorado, noting that Gardner supported a "personhood amendment" to limit abortion and suggesting he wanted to ban some types of birth control.

That led to criticism that Udall was running a "one-issue campaign," with Colorado voters wanting to hear more about the economy and jobs. It was tough to paint the affable Gardner as a radical, and when a Denver reporter jokingly dubbed Udall "Mark Uterus," it stuck.

Gardner also got a surprise endorsement from The Denver Post, which supported Udall six years earlier.

Supporters of Gardner point out that he voted for a bill in the House to block the bulk surveillance program, suggesting that there may not be much daylight between the candidates on the surveillance. Still, given Udall's position as a longtime critic—one on the Senate Intelligence Committee, no less—his departure will be a loss for those looking to rein in intelligence agencies.

"What Udall has is the institutional memory and the relationships in the civil liberties community, in the Democratic Party, and in the tech industry so that we don’t have to start over again with someone new," the head of ACLU's Washington DC office told The Hill.

The other longtime NSA critic on the Senate Intelligence Committee is Sen. Ron Wyden (D-OR), who was not up for reelection last night.