Republican Martha McSally on Monday conceded Arizona's U.S. Senate race to Democrat Kyrsten Sinema.

The win makes Sinema, who was first elected to the U.S. House from Arizona in 2012, the first openly bisexual person to be elected to the Senate.

Arizona voters have not elected a Democrat to the Senate in nearly a quarter century.

Sinema came from behind to overcome McSally's election night lead. As of Monday, Sinema was nearly 2 percentage points ahead of McSally.

“[W]e can work together to meet the challenges our country faces,” Sinema said in a tweet after the AP declared her the winner. “We can do this differently. For our country, for our future, for Sen. [John] McCain, and for each other I think we must.”

McSally conceded in a video message posted to Twitter.

“I just called Kyrsten Sinema and congratulated her on becoming Arizona's first female senator,” McSally told supporters.

The Human Rights Campaign (HRC), the nation's largest LGBT rights advocate, congratulated Sinema in a blog post, adding that it had poured additional resources into the Arizona race.

“Arizona voters rejected Donald Trump and Mike Pence’s politics of bigotry and fear and made history by electing bold pro-equality champion Kyrsten Sinema as the nation’s first openly bisexual U.S. Senator,” said HRC President Chad Griffin. “For more than a year, HRC has worked to organize 800,000 equality voters across the state and we are proud to have helped Senator-elect Sinema across the finish line in a tight race. We celebrate this incredible moment and look forward to rolling up our sleeves and getting to work with Sinema, and Arizona Congressmembers Tom O’Halleran, Ann Kirkpatrick, Raul Grijalva, Ruben Gallego, and Greg Stanton to move equality forward for all Arizonans.”