BREAKING: Dems tout first openly gay senator as Pappas defeats Sununu in NH

"This has been an incredible campaign," Sununu said in his concession speech, as reported by WMUR. "But this is not our night."

With Pappas replacing retiring Democrat Sen. Jeanne Shaheen, the New Hampshire victory is not a seat flip, but does close the door on one of the few Democrat tossup seats that Republicans had hoped to gain in an election cycle that was widely expected to favor Democrats.

Sununu, part of a prominent New Hampshire dynasty, was a popular governor but well known as a centrist and anti-Trump figure in a state where the president's popularity was deeply underwater.

Pappas, for his part, had downplayed his sexuality as a major campaign issue, according to USA Today.

"My campaign and my time in public service is always focused on what I can do for New Hampshire, how I can make people's lives better," he said. "So I'm not running to make history, but, you know, it's a sign that our nation has come a long distance."

While it is unclear how many previously gay senators there have been who were not open, the election of Pappas follows a campaign season in which Democrat activists sought to besmirch the late South Carolina Republican Sen. Lindsay Graham with allegations that he had paid male escorts for sex.

In a "documentary" titled "The CLOSETocracy," designed to smear Graham's reputation as a way to undermine his sister's reelection campaign, a man identified as "Kelvin," alleged that Graham paid him $120 for sex in 2001 at a property in Arizona. He said he was 17 at the time, Newsweek reported.

Rep. Barney Frank, a Massachusetts Democrat, was the first openly gay member of Congress, coming out in 1987 and serving Massachusetts in the US House.