The Pivotal Independent
Kyrsten Sinema’s six years in the Senate encompassed one of the most dramatic political transformations in recent American political history. She arrived in Washington in January 2019 as the first openly bisexual senator in American history and the first Democrat to win Arizona’s Senate seat since Dennis DeConcini in 1988. She was known for her triathlon training, her unconventional wardrobe, and her reputation as a pragmatic centrist who would work across party lines. Within three years she had become one of the most controversial figures in the Democratic Party — and within four years she had left it entirely.
The years 2021 and 2022 defined her legacy in ways she almost certainly did not intend. With Democrats holding a nominal 50–50 Senate majority after the Georgia runoffs, Sinema and Joe Manchin of West Virginia became the swing votes on virtually every consequential piece of legislation. Their objections killed the $3.5 trillion Build Back Better package — Biden’s signature domestic agenda — in its original form. Sinema specifically objected to raising corporate and top income tax rates, a position that infuriated the Democratic base and led to confrontations at her fundraisers, at Arizona State University where she taught, and eventually at the Phoenix airport where activists followed her into a restroom. She also blocked filibuster reform, preserving the 60-vote Senate threshold that Republicans used to block most Democratic legislative priorities. The combination made her the most unpopular Democratic senator among Democratic voters in any polling conducted during that period.
In December 2022, days after Democrats retained the Senate majority in the midterms, she registered as an Independent. She said she was tired of partisan games. The practical effect was to make herself immune to the Democratic primary challenge that Representative Ruben Gallego was openly preparing. She continued to caucus with Democrats for committee assignments but was no longer subject to party discipline. In 2024 she announced she would not seek re-election. Gallego won Arizona’s Senate seat comfortably, and Sinema left the Senate in January 2025 — a figure whose political career ended not with a defeat but with an exit that satisfied almost nobody.
Key Policy Areas
60-Vote Defender
Sinema’s most consequential position was her refusal to support eliminating or reforming the Senate filibuster. Her position — that the 60-vote threshold was essential to forcing bipartisan cooperation — effectively killed the John Lewis Voting Rights Act and the Freedom to Vote Act in 2022, as well as other Democratic priorities. She argued that majority rule without minority protections would accelerate partisan polarization.
Tax Rate Opposition
Sinema opposed raising the corporate tax rate and the top individual income tax rate in the Build Back Better negotiations, blocking one of the key revenue-raising mechanisms Democrats relied on to fund their domestic agenda. She ultimately voted for the Inflation Reduction Act, which used a 15% corporate minimum tax rather than a rate increase — a compromise specifically designed to win her support. Her position was widely interpreted as reflecting her Arizona donor base.
Infrastructure & Gun Safety
Despite her reputation as an obstructionist on the Democratic agenda, Sinema was a genuine bipartisan deal-maker on some legislation. She was a co-architect of the Bipartisan Infrastructure Law (2021) and helped negotiate the Bipartisan Safer Communities Act (2022) — the first significant federal gun safety legislation in nearly three decades. These achievements demonstrated that her centrist positioning produced real legislative outcomes in areas where partisan gridlock had previously been total.
Electoral History
| Year | Race | Result | Margin |
|---|---|---|---|
| 2024 | Arizona Senate | Did not seek re-election | — |
| 2018 | Arizona Senate | Sinema (D) 50.0% — Martha McSally (R) 47.6% | D +2.4 |
| 2016 | Arizona House (9th District) | Sinema 61.2% — Jennifer Wright (R) 38.8% | D +22.4 |
| 2014 | Arizona House (9th District) | Sinema 54.9% — Wendy Rogers (R) 45.1% | D +9.8 |
| 2012 | Arizona House (9th District, new) | Sinema 48.9% — Vernon Parker (R) 45.6% | D +3.3 |
| 2010 | Arizona State House | Re-elected to state legislature | D win |
From Green Party Activist to Independent Senator
Sinema’s ideological trajectory is difficult to categorize because it has moved in both directions simultaneously. In the early 2000s she was a Green Party activist who called the Iraq War immoral and participated in anti-war demonstrations in ways that her 2018 Senate campaign opponents surfaced as opposition research. She then moved to the center-left to win state legislative and congressional seats, presenting herself as a pragmatic Democrat willing to work across the aisle in a competitive district.
Her Senate years revealed a senator whose instincts leaned toward elite business interests and institutional process protection in ways her earlier progressive biography did not predict. Whether this represented a genuine evolution, opportunistic repositioning toward her donor base, or a consistent underlying philosophy of institutional incrementalism is a matter Democrats debated extensively during her tenure. Her exit from the Democratic Party settled the practical question — she would not be the vehicle for progressive politics in Arizona — but left the deeper question about her political identity unresolved. She remains one of the more enigmatic figures in the Biden-era Senate.
