Sen. Kyrsten Sinema, an Arizona independent, announced Tuesday she will retire at the end of her term this year, blaming growing partisanship and mudslinging in Washington for driving her decision to not run for reelection.

“I believe in my approach, but it’s not what America wants right now,” Sinema said, in a video announcing her decision.

Sinema’s decision takes her out of the fight for her seat in an extremely competitive state. Democratic Rep. Ruben Gallego of Arizona and former Arizona Republican gubernatorial nominee Kari Lake are among the candidates who had been seeking to challenge Sinema.

Sen. Steve Daines of Montana, who chairs the Senate GOP’s campaign arm, told CNN that Sinema’s decision not to run for reelection will help Lake’s candidacy.

“I wasn’t surprised by that announcement. And the polling shows that it actually gives somewhat of an advantage to Kari Lake, in all the polling we’ve done,” Daines said. “So it gives us another great opportunity, another open seat on the Senate map.”

Sinema has long been a high-profile and influential figure in the Senate, frequently working to broker compromise between Democrats and Republicans.

She formally left the Democratic Party in 2022 to register as a political independent, telling CNN’s Jake Tapper at the time, “I’ve never fit neatly into any party box. I’ve never really tried. I don’t want to.”

“Removing myself from the partisan structure – not only is it true to who I am and how I operate, I also think it’ll provide a place of belonging for many folks across the state and the country, who also are tired of the partisanship,” she said in that interview.

Most recently, Sinema served as a key negotiator, along with Republican Sen. James Lankford of Oklahoma and Democratic Sen. Chris Murphy of Connecticut, for a major bipartisan border deal that was intended to be paired with a foreign aid package with assistance for Ukraine and Israel.

Senate Republicans initially demanded that any foreign aid package be passed along with border measures, but ultimately turned against the border deal and blocked it amid harsh criticism of the package from former President Donald Trump. The Senate went on to pass a foreign aid package with aid for Ukraine and Israel without border provisions, but House Speaker Mike Johnson has said he does not plan to bring the bill to the floor and many House Republicans oppose further aid for Ukraine.

This story has been updated with additional developments.