WASHINGTON—Sen. Kyrsten Sinema of Arizona, a pivotal centrist who has helped broker bipartisan deals and forced changes to major pieces of President Biden’s agenda, said she was leaving the Democratic Party and would register as an independent, a move that complicates Democrats’ narrow control of the chamber.
The move sent a jolt through Washington just days after Democrats secured their 51st seat in the chamber by winning a runoff election in Georgia. It raised questions about how closely Ms. Sinema would align with the party in the second half of Mr. Biden’s term and introduced a new wrinkle in the outlook for the 2024 election, when Democrats are facing a tougher Senate map than in 2022.
“I have joined the growing numbers of Arizonans who reject party politics by declaring my independence from the broken partisan system in Washington,” she wrote in an opinion article in the Arizona Republic announcing her exit from the party. “Showing up to work with the title of independent is a reflection of who I have always been,” she said in an accompanying video. “Nothing’s going to change about me.”
Ms. Sinema didn’t say in her opinion article or the video whether she would caucus with Democrats, but she is keeping her committee assignments controlled by the Democrats and signaled that the move won’t change the way she votes or works in the Senate. Sens. Bernie Sanders of Vermont and Angus King of Maine are both independents but caucus with Democrats and are counted as part of their majority.
In an interview with CNN, Ms. Sinema said questions about whether the Democrats’ majority would remain at 51-49 or effectively become 50-49 was “kind of a D.C. thing to worry about.”
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