Sen. Kyrsten Sinema announced this week that she plans to register as an Independent, formally leaving the Democrat party.

In an op-ed published in the Arizona Republic, Sinema announced her intention to change parties. “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. 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.”

She now joins two other Senate Independents: Sen. Bernie Sanders (I-VT) and Angus King (I-ME). Sens. Sanders and King caucus with the Democrats.

Sinema has said she would not caucus with Republicans, but has not explicitly said she will continue to caucus with Democrats. With Democrats maintaining control of the Senate, Sinema has said she expects to continue to hold her subcommittee chairmanships. She currently chairs the Senate Homeland Security Subcommittee on Government Operations and Border Management as well as the Senate Commerce, Science, and Transportation Subcommittee on Aviation Safety, Operations, and Innovation.

Committee assignments for the 118th Congress have largely not been named yet, although it is traditional to continue serving as chair if desired and the incumbent party maintains control of the chamber.

Sinema served three terms in the U.S. House of Representatives as a Democrat and won election to the Senate in 2018 as a Democrat.