Kyrsten Sinema announced that she will step down from the Senate at the end of the year, rather than run for re-election, in a video published on Tuesday, 5 March.
The senator from Arizona said she was choosing to leave “because I choose civility, understanding, listening, working together on stuff”.
Ms Sinema was a Democrat, but switched to be independent in 2022.
Her decision makes the border state’s politics likely to be it one of the most talked-about parts of the country as the presidential election nears, as her presence in the 2024 race was likely to set up a three-way fight between herself and the two major-party challengers for her seat.