The answer is likely related to her 2024 prospects.
To put it mildly, Sinema has not endeared herself to Democrats in her home state. Earlier this year, Data For Progress polled Arizona Democrats and found the incumbent senator trailing Gallego in a hypothetical primary match-up, 74% to 16%. That’s not a typo: She actually trailed the popular congressman by 58 points.
With this in mind, Sinema very likely realized that she had a decision to make: She could (a) retire; (b) take steps to repair the relationship with the Democratic voters who elected her in the first place; or (c) take her chances as an independent.
As a tactical matter, settling on the third option makes sense. Sinema was very likely to lose a Democratic primary, her voting record made a run as a Republican implausible, and she didn’t want to walk away from Capitol Hill altogether. Becoming an independent is a sensible strategy.
Indeed, it’s not unrealistic to think it might very well save her career. Democrats will likely think twice about running a candidate against her in 2024, fearing that splitting the center-left mainstream could leave the seat in Republican hands. Sinema’s announcement probably won’t dramatically alter the makeup of the Senate, but if it neutralizes an electoral threat, it’ll give the senator what she’s looking for: a re-election edge she wouldn’t otherwise have.
But as the political world digests the news, it’s also worth pausing to appreciate Sinema’s bizarre ideological trajectory. In the Bush/Cheney era, she was a liberal activist and failed Green Party candidate who railed against then-Sen. Joe Lieberman as a “pathetic” sellout.
Twenty years later, Sinema has done exactly what Lieberman did: become an independent while caucusing with Senate Democrats