Senate Democrats were livid after Sens. Kyrsten Sinema (I-Ariz.) and Joe Manchin (I-W.Va.), two longtime members of their caucus, voted Wednesday to block President Biden’s nominee, Lauren McFerran, to serve another five-year term on the National Labor Relations Board.

Senate Democrats blasted their votes to sink Biden’s nominee and hand Republicans a major victory as “pathetic” and “disappointing.”

Sen. Kyrsten Sinema (I-Ariz.) announced on Tuesday that she will not seek reelection this year, opting out of what would have been a contentious, three-way contest in a swing state that will be consequential for the political balance of the U.S. Senate.

Cut through the 2024 election noise. Get The Campaign Moment newsletter.

Here’s what to know about how Sinema’s decision shakes up the race.

Who is running?

Arizona Sen. Kyrsten Sinema announced what has been obvious for a while now. She’s not running for reelection.

Sadly, I doubt there will be many around the state who will miss her.

She was the first Arizona Democrat in three decades to win a U.S. Senate seat, campaigning on a pledge to work with anybody to get stuff done.

Since then, she’s done just what she promised. She charted a middle course, in search of solutions that have bipartisan support.

Then she learned a hard lesson.

Sen. Kyrsten Sinema’s (I-AZ) decision not to seek reelection to the Senate puts Rep. Ruben Gallego (D-AZ), the likely Democratic nominee, and Kari Lake, who is the front-running Republican candidate, on the fast track for a two-way race in Arizona.

Immediately following the news of Sinema’s retirement, Sen. Steve Daines (R-MT), the leader of the GOP Senate campaign arm, declared the development would improve Lake’s opportunity to flip the seat. 

Independent Senator Kyrsten Sinema of Arizona has announced she will not run for re-election in November.

She decided to leave the Senate "because I choose civility, understanding, listening, working together on stuff", she said.

Ms Sinema switched from being a Democrat to an independent in 2022 but typically votes with her former party.

This sets up a straight fight between Republicans and Democrats, who narrowly control the upper chamber.

It is unclear which party benefits more from her announcement.

Sen. Kyrsten Sinema announced on Super Tuesday that she will not seek reelection when her first term ends next year.

The move from Sinema, an Arizonian who switched her party affiliation from Democrat to independent in 2022, leaves the race narrowed between Republican candidate Kari Lake and Democrat Ruben Gallego.

"Our democracy was weakened by government dysfunction and the constant pull to the extremes by both political parties," Sinema said in a video announcement posted to X, the platform formerly known as Twitter. "I promised I would do my best to fix it."

Sen. Kyrsten Sinema, an Arizona independent, announced Tuesday she will leave the Senate at the end of her term this year, a move that will shake up the battle for control of the chamber in November and remove a key player who has been central to major negotiations in Congress.

Sinema has been an influential yet polarizing figure in the Senate and has frequently worked to broker compromise between Democrats and Republicans. In announcing her decision not to seek reelection, the Arizona senator said, “I believe in my approach, but it’s not what America wants right now.”

Sen. Kyrsten Sinema (I-Ariz.) is opting against running for reelection, providing Democrats a sigh of relief and avoiding what would have been a messy three-way race with an independent incumbent, a Democrat and a Republican.

Sinema made the announcement in a video on social media, arguing that voters aren’t interested in electing members focused on compromise. 

Sen. Kyrsten Sinema (I-AZ) is facing an ethics complaint from a conservative watchdog group over allegations of her "long-standing and ongoing failure to fully complete" financial disclosures.