PHOENIX — U.S. Sen. Kyrsten Sinema is growing increasingly isolated from some of her party’s most influential officials and donors after playing a key role in scuttling voting rights legislation that many consider essential to preserving democracy.

Leaders of the Arizona Democratic Party voted Saturday to censure Sinema, citing “her failure to do whatever it takes to ensure the health of our democracy” — namely her refusal to go along with fellow Democrats to alter a Senate rule so they could overcome Republican opposition to the bill. While the rebuke is symbolic, it is striking given that only three years ago, Sinema was heralded for bringing the Senate seat back into the Democratic fold for the first time in a generation.

Donors are threatening to walk away. Several groups are already collecting money for an eventual primary challenge, even though she’s not on the ballot until 2024. Young activists are holding a second hunger strike to draw attention to Sinema’s vote.

The moves offer a preview of the persistent opposition Sinema will likely face within her own party in the two years before she next appears on a ballot. The independent streak that has given her tremendous leverage over the agenda in Washington has enraged many Democrats back home who are intent on preventing her reelection.

“Any reservoir of goodwill that she had is gone,” said Rep. Ruben Gallego, an Arizona Democrat who may challenge Sinema from the left.

Sinema’s defenders say nobody who’s watched her for the past decade should be surprised by her position. She often bucked her party in the House, ran an aggressively moderate campaign for Senate and has never wavered in her support for upholding the filibuster.

“During three terms in the U.S. House, and now in the Senate, Kyrsten has always promised Arizonans she would be an independent voice for the state — not for either political party,” Hannah Hurley, Sinema’s spokesperson, said in a statement before the censure vote. “She’s delivered for Arizonans and has always been honest about where she stands.”

Hurley repeated her comments in response to the censure.

Sinema’s influence is driven by the Senate’s 50-50 split, which essentially gives any senator the ability to kill legislation, an option Sinema has repeatedly exercised.

But she faces political dynamics unlike the other Senate moderate thwarting Democratic ambitions, Joe Manchin of West Virginia. Representing a state that former President Donald Trump carried by nearly 39 percentage points in 2020, Manchin is unlikely to face a progressive challenger who would gain traction.