With little fanfare, Sen. Lisa Murkowski (R-Alaska) on Thursday filed her candidacy paperwork for a Senate run in 2022.
The Alaska Republican, 64, had been mum about whether she planned to seek reelection to a fourth term. She told Politico in June, "I have not made public my intentions."
But the paperwork she filed with the Federal Election Commission does:
Murkowski is a rare politician in today's Senate: a moderate with record of working with Democrats on a number of fronts, and someone who is not afraid to buck her party on major votes.
She was arguably the most pivotal vote against repealing the Affordable Care Act in 2017. She was the only GOP senator who opposed Brett Kavanaugh's confirmation to the Supreme Court in 2018. She regularly condemned former President Donald Trump for his dangerous rhetoric and attacks on the media.
In January, Murkowski was one of Republican senators who voted to convict Trump on an impeachment charge of inciting the violence at the U.S. Capitol. She's the only one of those seven senators up for reelection in 2022 and she's a prime target of Trump's. He is already backing her GOP challenger, Kelly Tshibaka.
But the three-term senator has proven she's a tough candidate to beat.
She's got the support of national Republicans, including Senate Minority Leader Mitch McConnell, and strong name recognition across her state. In a stunning victory in 2010, she won reelection as a write-in candidate after a Tea Party insurgent defeated her in the GOP primary.
Murkowski won her last election by 15 points in 2016, despite never endorsing Trump.
She may represent a red state, but her base of supporters is not conservative Republicans. It is a mix of moderate Republicans, Democrats and independents, and she's kept many of those supporters with her for the better part of 18 years (she was initially appointed to her Senate seat in December 2002).
"Out of 100 members in the Senate, she's the only one that's really wearing the balls right now," Carroll Knutson, a 74-year-old Republican resident of Soldotna, Alaska, told HuffPost in 2017. "I don't know if you can put that in your story."
This article originally appeared on HuffPost and has been updated.