Sen. Kyrsten Sinema (Ariz.) said Friday that she is switching her party affiliation from Democrat to independent, creating a shake-up in the chamber after the midterm elections.

“Registering as an independent and showing up to work with the title of independent is a reflection of who I’ve always been, and it’s a reflection of who Arizona is,” Sinema said in a video. “We don’t line up to do what we’re told. We do what’s right for our state and for our country. I’m going to be the same person I’ve always been.”

With the move, Democrats will still control the Senate next year, but their hold could be less secure and give more sway to another moderate in the caucus, Sen. Joe Manchin III (D-W.Va.). In an op-ed in the Arizona Republic, Sinema — who has voted with President Biden more than 90 percent of the time — said that she never promised to be a guaranteed vote for the Democratic Party.

“Americans are told that we have only two choices — Democrat or Republican — and that we must subscribe wholesale to policy views the parties hold, views that have been pulled further and further toward the extremes,” she wrote. “Most Arizonans believe this is a false choice, and when I ran for the U.S. House and the Senate, I promised Arizonans something different.”

Sinema, a first-term senator who has broken with her party on some key issues, did not explicitly say she will continue to caucus with Democrats in an interview with CNN. But as long as she does not caucus with Republicans, as she told Politico she wouldn’t, the GOP side in the chamber would remain in the minority with 49 members.

A spokeswoman for Sinema, Hannah Hurley, told The Post that the senator intends to continue receiving her committee assignments from the Democrats.

“I don’t anticipate that anything will change about the Senate structure,” Sinema told Politico. “I intend to show up to work, do the same work that I always do. I just intend to show up to work as an independent.”

Sinema has modeled her Senate tenure on that of the late Sen. John McCain (R-Ariz.), a GOP maverick. She has angered quite a few Democrats in the Grand Canyon state, so much so that she was likely to face a Democratic primary challenge in a 2024 reelection bid. The lawmaker has been repeatedly criticized by the Democratic Party’s base for not being on board with core liberal priorities, including increasing the minimum wage.

Last January, leaders of the Arizona Democratic Party voted to censure Sinema. They cited “her failure to do whatever it takes to ensure the health of our democracy” — namely her refusal to go along with fellow Democrats to alter the Senate rule so they could overcome Republican opposition to a voting rights bill.

At the same time, Sinema has helped deliver several bipartisan wins for President Biden, most notably on infrastructure and gun control, and has been a consistent vote for the president’s administration and judicial nominees. But she has balked at efforts to ditch the filibuster for voting rights and other legislation in the closely divided Senate.

In a statement Friday, White House press secretary Karine Jean-Pierre called Sinema a “key partner on some of the historic legislation President Biden has championed over the last 20 months,” including the infrastructure law, a semiconductor chips measure and a sweeping climate and health-care bill.

“We understand that her decision to register as an independent in Arizona does not change the new Democratic majority control of the Senate, and we have every reason to expect that we will continue to work successfully with her,” Jean-Pierre said.

Sinema’s announcement comes days after the Senate’s Democratic caucus claimed 51 seats with the reelection of Sen. Raphael G. Warnock (D-Ga.). The group includes two independents — Sens. Bernie Sanders (Vt.) and Angus King (Maine) — who caucus with the Democrats.

Sinema informed Senate Majority Leader Charles E. Schumer (D-N.Y.) of her decision on Thursday, according to Politico.

Sen. Chris Murphy (D-Conn.) said Friday that he was not surprised by the news given Sinema’s independent streak and did not believe it would change the organization of the Senate or how Sinema votes in the future.

“I take Kyrsten at her word that this doesn’t change how she votes and doesn’t change anything about her values or beliefs. She’s always been an independent thinker,” he said. “This seems like this changes the letter next to her name and not much else.”

Sinema, 46, ran for the Phoenix City Council more than 20 years ago on the Green Party ticket, served in the House and broke the GOP grip on Arizona in 2018 when she won the Senate seat, defeating Martha McSally (R). During her Senate tenure, her willingness to break with her party on key issues has drawn praise from the other side of the aisle.

Senate Minority Leader Mitch McConnell (R-Ky.) invited Sinema to speak at the McConnell Center at the University of Louisville in September, calling her the “most effective first-term senator” he has seen in his nearly 40-year Senate career.

“She is, today, what we have too few of in the Democratic Party: a genuine moderate and a dealmaker,” he said.

That appearance, in the heat of the midterm election campaign, angered Rep. Ruben Gallego (D-Ariz.), a potential challenger to Sinema in 2024, who wrote on Twitter, “I mean you could be out there helping our candidates @SenatorSinema But my sense is that you would actually prefer the Dems lose control of the Senate and House.”

On Friday, Gallego blasted Sinema’s move to switch party affiliations from Democrat to independent, suggesting it was self-serving politically and could hurt her leverage in the Democratic-controlled Senate.

“At a time when our nation deserves leadership most, Arizona deserves a voice that won’t back down in the face of struggle,” Gallego said. “Unfortunately, Senator Sinema is once again putting her own interests ahead of getting things done for Arizona.”

In her interviews, Sinema did not say whether she would seek reelection in 2024. In announcing her switch in party affiliation, she avoids a direct challenge from Gallego in the Democratic primary, but her move scrambles an all-but-certain competitive race if both parties nominate candidates.

During her first run for the U.S. Senate in 2018, Sinema tailored her campaign to undecided voters and independents. She avoided party labels and events, frequently wore purple and closed the race with a rare one-minute TV ad with a theme of working beyond partisan lines. “She’s independent, just like Arizona,” the ad said.

In freeing herself of a party label, Sinema, should she choose to run for reelection, averts what could be a nasty primary contest in a battleground state almost evenly divided between Republicans, Democrats and independent voters.

“What she’s going to have to do is win 40 percent of Republicans, 40 percent of Democrats and 60 percent of independents,” said Chuck Coughlin, a GOP consultant in Arizona. “It realigns who you’re marketing to, and the reason most people don’t do it is because you can’t afford to have a primary going on where you’re ignored.

“Well, she’s not going to be ignored, we know this. She’ll be sitting there, waiting,” he added.