Arizona senator Kyrsten Sinema’s announcement that she’s leaving the Democratic Party to become an independent is fully consistent with her trajectory throughout her political career.

She first became politically active in the Green Party as a critic of capitalism. She ran for the Arizona legislature on the Green ticket, calling herself a “Prada socialist” and finishing last in a five-candidate field. Switching to the Democratic Party, she won a seat in the state legislature in 2004, and then was elected to the US House in 2012 and to the US Senate in 2018. She’s now decided that she’s an independent. But the reality of her move is that it’s a boost to Republicans.

Sinema, who remains the first out bisexual person ever elected to the upper chamber, will become the third independent in the Senate. The two others — senators Bernie Sanders of Vermont and Angus King of Maine — are both very popular in their states and caucus with the Democrats. In contrast, Sinema is extremely unpopular among Arizona voters and hasn’t said whether she’ll caucus with the Democrats or Republicans.

Most likely, she won’t caucus with either party, hoping that Democratic majority leader Chuck Schumer and Republican minority leader Mitch McConnell will each have to beg her to support his party’s agenda — making her the center of attention, which is what she craves more than anything else.

Even without her, the Democrats will have fifty votes in the upper chamber, allowing them (with Vice President Kamala Harris’s tie-breaking vote) to support Biden’s nominees for the federal branch and support other bills that can’t be stopped by a filibuster — but only if all fifty Democrats (including rogue senator Joe Manchin of West Virginia) vote as a bloc.

In November, Arizona Democrats swept statewide offices. Arizonans reelected a Democratic senator (Mark Kelly) and elected a Democratic governor (Katie Hobbs), a Democratic secretary of state (Adrian Fontes), and (pending a recount) a Democratic attorney general (Kris Mayes).

Why would Sinema buck that trend and leave the Democratic Party? The answer is simple: she’s playing chicken with Arizona Democrats, hoping to scare away any Democrat from running against her, knowing that she’d lose. She’s essentially trying to hold the Democratic Party, and Democratic voters, hostage.

When she ran for Senate in 2018, all the liberal and progressive groups — unions, environmentalists, Latino and immigrant rights activists, gay rights advocates, and feminists — backed her. Since then, she’s been a traitor to their causes and unaccountable to the people who did the work of putting her in office. She’s even refused to meet with unions whose members knocked on doors and made phone calls to help her win.

Instead, she’s been an ally of big business. Along with Manchin, Sinema has been a constant thorn in the side of President Biden and fellow Senate Democrats, refusing to vote for major Democratic bills and making it difficult for Biden and the Democrats to pass several parts of their agenda that are popular and progressive.

She collected huge contributions from drug companies, Wall Street, the Chamber of Commerce, the Business Roundtable, the National Association of Manufacturers, and other corporate lobby groups. With that backing, she opposed the provisions of Biden’s Build Back Better bill that big business opposed, including higher taxes on corporations. She helped thwart the Democrats’ plan to cut drug prices. She voted against raising the federal minimum wage to fifteen dollars an hour — a key part of the Democrats’ agenda and one that polls show is very popular among Democrats and independents alike.

A bipartisan poll in September by Fabrizio Ward and Impact Research found that only 37 percent of Arizona voters — including 37 percent of Democrats, 36 percent of Republicans, and 41 percent of independents — had a favorable opinion of her.

She is so unpopular that it has been clear she will face a primary challenge when she’s up for reelection in 2024. Her most likely challenger is Representative Ruben Gallego, a progressive Democrat. A January poll by Data for Progress found that in a Democratic primary, she would lose to Gallego 74 percent to 16 percent.

“I am not surprised. But I’m still shockingly disappointed at how awful she continues to be,” Michael Slugocki, an outgoing vice chair of the Arizona Democratic Party, told NBC News. Sinema, he said, has had “no relationship and no contact with the state party for months” and did not inform Democratic leaders about her decision to leave the party. “She’s deliberately trying to make it difficult for Democrats in Arizona,” Slugocki said.

Switching to independent is an attempt to prevent Gallego from running for her seat. She’s assuming that if she runs as an independent and Gallego runs as a Democrat in November 2024, they will split the votes of non-Republicans. As a result, a Republican will be elected as Senator from Arizona. She’s trying to scare Gallego (or any other Democrat) into avoiding that scenario by not running against her and whomever the Republicans nominate for Senate, giving her a chance to win reelection as an independent.

Of course, we don’t know who the GOP candidate will be. The likely contenders for the Republican nomination are Kari Lake (who narrowly lost her race for governor last month), Blake Masters (who lost the Senate race to Mark Kelly), and Mark Lamb (who was elected Pinal County Sheriff in 2016 and 2020). Each were endorsed by Donald Trump. In a two-way race, would Sinema beat a MAGA Republican? In a three-way race, would Sinema prevail over a liberal Democrat (Ruben Gallego) and a MAGA Republican?

Perhaps Gallego has a better chance than Sinema to beat a MAGA Republican. If, as expected, Gallego announces that he will run for the Democratic nomination for Senator, his goal would be to turn the tables on Sinema by forcing her to withdraw from the race, knowing she can’t win.

If polls show that a Republican has 40 percent support, Gallego has 40 percent support, and Sinema has 20 percent support, she might withdraw. But she’s so unpredictable and irresponsible that she might run anyway.

We’ll see how she conducts herself in the Senate over the next year, but it is likely that she’ll try to cast herself as “bipartisan” or “nonpartisan” and vote on some bills with Democrats and on other bills with Republicans. That is likely to anger more Arizona voters than attract them to support her in 2024.

In the short term, Sinema has gotten what she wants: attention. But attention isn’t the same as popularity.

If she does play a “spoiler” role and is widely hated by Democrats and independents, leading to a GOP victory, it is possible that the Republicans will reward her with some cushy K-Street lobbying job. Then again, who would want to be seen having lunch with her?