When Kyrsten Sinema campaigned for the Senate as an independent voice for Arizona, her volunteers didnt take that literally. Perhaps they heard what they wanted to hear. Ana Doan, a retired teacher, thought Sinema would bring fresh energy to Washington as Arizonas first openly LGBTQ senator. Devina Alvarado, a young Costco forklift driver, thought Sinema would defend womens rights from Donald Trump. Michael (identified by his middle name to avoid retaliation) admired that Sinema had made it out of poverty after experiencing homelessness as a child, as he did. Each from a different corner of Arizona, they were all proud to have volunteered to get Sinema elected, proud of the doors theyd knocked and calls theyd made, proud to have had her glossy purple-and-yellow literature scattered in their home or on the floor of their car. But their pride had curdled long before Sinema announced she was leaving the Democratic Party last Friday.

So far, both the White House and Sinemas Senate colleagues have been conciliatory, praising her legislative skill and acting as if little will change following her switch. (Sinema will still caucus with the Democrats.) Although her influence will diminish in a forthcoming 5149 chamber, Democrats can ill afford to make Sinema a pariah. When reached for comment about the switch, Sinemas press secretary told me in an email, Kyrstens approach remains the same from when she first ran for Senate, and directed me to a sleek video Sinema released on Friday: Im gonna be the same person Ive always been, the senator said.

But many of her most dedicated supporters dont see things that way. I spoke with dozens of Sinemas former volunteers from across Arizona, some of whom I managed in 2018 as a field organizer for the Arizona Democratic Party. What theyve described to me is a feeling more raw and pained than mere disagreement over policies. Arizona Democrats are used to that; many have Republicans and independents in their family. Theyre used to talking through differences. What they cannot forgive is the feeling that Sinema was not straight with them.

David A. Graham: Kyrsten Sinemas decision is all about 2024

Doan, the teacher, had worked on a lot of campaigns in the border town of Nogales. She had just retired when Sinema announced her run, and she threw herself into the Senate race. Sinema was smart, well-spoken, a member of the LGBTQ community, and a fundraising powerhouse. In previous elections, Doan had begged the state party to do more phone banking in Spanish, and she didnt like that phone bankers rushed older Latino voters who had questions about important issues. Things were different on Sinemas campaign. Doan could have phone-bank lists brought to the houses of other volunteers, so they could make calls from the comfort of their own home.

She was thrilled when Sinema won, but her excitement was short-lived. Sinema, in her view, started spending too much time with the Big Business people who had funded her campaign and not enough time among the working-class folks whod made phone calls for her. Doan told me it hurt to watch her senator block positive initiatives that other Democrats wanted to pass. She made an idiot out of me, and I made an idiot out of all the people I spoke to, Doan said. She said she wished Sinema had run as an independent in 2018, so people knew who she really was.

Alvarado, the forklift driver, had never volunteered on a political campaign before. She canvassed for Sinema a few days a week after finishing work and on the weekends too, always wearing her pink Planned Parenthood shirt. Alvarado couldn’t believe it when Sinema said she thought protecting the filibuster was essential to protecting womens rights. When Sinema comes up in conversation these days, Alvarados fianc teases her. He knows Im super salty that I volunteered for her, she told me. I for sure look forward to canvassing for her opponent.

Michael considered Sinema to be a personal hero when he started volunteering on her campaign in Phoenix. A few years before, hed been homeless, just as she had been. But Michael felt betrayed in March of 2021, when Sinema voted against raising the minimum wage to $15 an hour. Hunger changes people, he wrote to me in an email. It made me want to make no one feel that way. Im guessing it made her protective of what she has.

Some of the people with the fewest illusions about Sinema were the people furthest away from her. Missa Foy, the chair of the Navajo County Democrats, didnt even vote for Sinema in the primary. In 2018, she knocked on more than 1,000 doors for a ballot initiative in Navajo County, one of Arizonas most rural regions. (You cant walk down the sidewalk to the next house on your list in Navajoyou get back in your truck and drive there.) The voters Foy spoke with would offer her dinner and shelter from the cold, and listen to why they should oppose programs such as expanding school vouchers. Although Foy passed out the Democratic slate of candidates, with Sinema on top, she didnt talk her up. Foy told me she was grateful for all the things that Democrats, including Sinema, were able to pass through the Senate, but she didnt think Sinemas new party preference was earth-shattering stuff. Our mission is the same as before this news broke, she said.

When Sinema visited Hopi sovereign land in 2018, Karen Shupla was impressed by her familiarity with water rights and other issues important to Native Americans. A tribal-elections registrar, Shupla is scrupulously neutral, but she does volunteer hundreds of hours to make sure elections run smoothly in a region that Democrats carry by more than two to one. She was unsurprised when the Hopi and other tribes supported Sinema by broad margins, and she was indifferent about Sinema becoming an independent. It depends on how she deals with Natives from here on out, Shupla told me. We dont want to be guessing which side shes going to take on matters.

Read: The deepening mystery of Kyrsten Sinema

The volunteer I spoke with over the weekend who still has the most affection for Sinema was the one who knew her personally. Martha Marty Bruneau met Sinema when the two of them ran for different seats in the Arizona state legislature in 2000. I never ran again, and she never lost again, Bruneau told me. The two of them stayed in touch. Bruneau thinks her fellow progressive Democrats have been exasperating and believes they put too much pressure on Sinema, who votes with Biden more than 90 percent of the time. She told me she doesnt get Sinemas reputation for being unapproachable. When I asked her if shed support Sinema over a Democratic challenger, Bruneau praised Sinemas record and said shed have to look at both candidates. This was, in dozens of interviews, the closest that any of Sinemas former volunteers came to saying they would vote for her again.

Some believe that Sinema is becoming an independent because she cant win against a primary challenger. Campaigning as an independent worked in Alaska for Lisa Murkowski in 2010, and in 2006 for Joe Lieberman in Connecticutbut they were running in deep-red and deep-blue states, where their party was dominant enough to form a coalition with voters from other parties. Arizona is purple, with roughly equal portions of Republicans, independents, and Democrats. Sinema positioned herself as a lone politician capable of uniting her state, but if she is reelected, it will likely be by forcing an expensive and vicious election.

As David A. Graham wrote in The Atlantic last week, Sinemas move is flashy but comes from a place of weakness. She seems vulnerable to a challenge from not only the left but also the center. Arizona just elected a full slate of establishment Democrats in a year far less favorable than 2018, when Sinema won her seat. Its unclear if the campaign arm of the Senate Democrats will even support her next time around. Whats more, 2024 is a presidential-election year in an era when split-ticket voting is rare. Although Sinema is an incumbent, her sour relationship with the Arizona Democrtic Party means she will not benefit from party infrastructure, for fundraising or mobilization. They dont know what to expect from her, and she feels no obligation to explain publicly what she believes, or why she believes it. Thats her prerogative. But its also the prerogative of people who lent Sinema their time and reputation to now turn against her. In bitter irony, the volunteers who cut their teeth working to get her elected may be among those working the hardest to defeat her.