(Bloomberg) -- Arizona Senator Kyrsten Sinema declared as an independent Friday but made clear she won’t caucus with Republicans, maintaining Democrats’ newly expanded control of the chamber, committee subpoena power and ability to advance judicial nominees.

Sinema, who has been a swing vote on key issues, said she would continue her centrist voting record, which has angered some Democrats in her home state who have vowed to mount a primary challenge if she seeks reelection in 2024.

“Becoming an independent won’t change my work in the Senate; my service to Arizona remains the same,” she wrote in an op-ed in the Arizona Republic. 

Sinema, 46, was first elected to the Senate in 2018 and was censured by the state party in January over her refusal to do away with the filibuster to force through voting rights legislation. The White House, however, stressed on Friday Sinema’s work on the bipartisan infrastructure bill and legislation to boost the domestic semiconductor industry. 

“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,” White House press secretary Karine Jean-Pierre said in a statement. 

Her action does come with political risks, however. If she runs again in 2024, a three-way general election race likely would benefit Republicans in narrowly divided Arizona.

Sinema becoming an independent won’t affect the overall control of the Senate next year. Her office said she intends to keep her committee assignments from the Democratic majority. And she doesn’t intend to caucus with the Republicans.

Jessica Taylor, the Senate editor of Cook Political Report said Democrats will still have the 51-49 seat control they secured earlier this week with Senator Raphael Warnock’s reelection in Georgia. 

“Democrats have more cushion than they had before,” Taylor said.

That majority gives Democrats expanded subpoena power next year, which they’ve said they intend to use for oversight and investigations of corporate actions.

Democrats still will either need Sinema’s backing on votes to confirm important nominees opposed by the GOP, or that of West Virginia Senator Joe Manchin, the conservative Democrat who also would face voters in the next election if he seeks another six-year term. 

That means the duo will continue to hold significant power in a divided Washington where President Joe Biden’s executive authority will play a big role with little prospect Democrats will be able to get legislation through the GOP dominated House next year.

Both Sinema and Manchin have reliably voted with their party for Biden’s judicial nominees. Senate Majority Leader Chuck Schumer said this week that a key focus on the chamber next year will be moving more of Biden’s picks to the bench. 

Manchin has repeatedly insisted he does not intend to become a Republican and this week was named to a post on Schumer’s leadership team. Becoming an independent would likely dilute his support in West Virginia and weaken his reelection chances. Manchin, 75, has not said whether he will run again.  

Sinema notified Schumer about her decision on Thursday, according to a Democratic aide. 

In a statement, Schumer said he agreed to Sinema’s request to keep her committee assignments.

“We will maintain our new majority on committees, exercise our subpoena power, and be able to clear nominees without discharge votes,” the New York Democrat said.

Despite breaks with Democrats on a few key issues, including raising corporate taxes, Sinema has voted with the party 97% of the time, according to data compiled by Bloomberg Government. She also has been a consistent vote in favor of Biden’s judicial nominees.

A political action committee dedicated to ousting her, called “Primary Sinema,” said in a statement that her move confirmed that she is “simply out for herself.”

“In one way, Sinema just made our jobs easier by bowing out of a Democratic primary she knew she couldn’t win. Now, we’ll beat her in the general election with a real Democrat,” the group said in a statement.

Last month, Democrats won in key races across the once-reliably Republican state, including governor, secretary of state and Arizona’s other US Senate seat. 

There are two other independents in the Senate, Bernie Sanders of Vermont and Angus King of Maine. They have divergent political stands but both caucus with Democrats on matters of the chamber’s organization and consistently vote with the party. Having a third independent in the Senate has no recent precedent.

The most consequential switch in recent times was Republican Jim Jeffords of Vermont becoming an independent and caucusing with Democrats in 2001, giving them the Senate majority. And after Senator Joseph I. Lieberman lost his Democratic primary in 2006, he won reelection anyway, and caucused with Democrats as an “independent Democrat.”

(Add statement from Schumer in 16th, 17th paragraphs)

©2022 Bloomberg L.P.