Why did Sinema ditch the Democrats? Here's a hint: It's not about ugly partisan games.

Sen. Kyrsten Sinema knows how to throw a punch.

On Friday, she officially ditched the Democratic Party and announced she has registered as an independent. The move wasn't entirely a shocker, yet it was still a gut punch for Arizonans who worked hard to send a Democrat to Washington.

“Everyday Americans are increasingly left behind by the national parties’ rigid partisanship, which has hardened in recent years,’’ she wrote in an exclusive column for The Arizona Republic.

She’s right about that. A third of Arizona’s electorate is registered as independents. Too many people just don’t fit inside the “tent” of the Democratic Party or the fragmented Republican Party.

“Pressures in both parties pull leaders to the edges – allowing the loudest, most extreme voices to determine their respective parties’ priorities, and expecting the rest of us to fall in line,” she continued.

She’s right about that, too. The loudest Americans espousing the most extreme views suck all the oxygen in the room, leaving everyone else disenchanted, lost and worried about the future of our country.

Leaving the party is a political move

Sinema doesn’t take responsibility for any of that and instead tries to portray herself as the victim of partisan “divisive, negative politics.”

Arizonans “are eager for leaders who focus on commonsense solutions rather than party doctrine,” she wrote.

She’s no victim. She’s ditching the Democratic Party because she either figured she can’t win a primary or she no longer needs the party’s money and infrastructure for her next move – or both.

Her trajectory suggests she’s adept at ditching anyone or anything no longer useful to her. She began her public life as a Green Party activist. That went nowhere so she became an independent, which didn’t work, either. Her big break came after she conveniently became a Democrat.

Her rejection of “party politics” and breaking away “from the broken partisan system in Washington” is just another one of her political moves.

“I committed I would not demonize people I disagreed with, engage in name-calling, or get distracted by political drama,” she wrote.

'I promised Arizonans something different': Sinema on registering as an independent

This is from the senator who became a political force in Washington by creating all sorts of drama and attention-grabbing stunts on the Senate floor with her thumbs-down vote on minimum wage and posting social media pictures with messages telling constituents to f--- off.

Sinema must figure she can't win a primary

Perhaps leaving the party at this particular juncture is tacit acknowledgmentthat she has angered so many Democrats to the point she no longer feels she can win a primary – should she seeks reelection in 2024.

She doesn’t indicate whether she’ll seek the seat, but either way she has calculated that ditching Democrats is her best political move.

Undoubtedly, she’s counting on independents and Republican support to retain her seat – whether those same Republicans who now profess their love for her would actually give her their spot is questionable at best.

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But forget her political future for a second. Most pressing is what her departure means for the Democrats’ slight Senate majority.

This week’s runoff victory of Raphael Warnock in Georgia gave Democrats a 51-49 advantage over Republicans. Sinema’s departure puts Democrats back at 50, which means Vice President Kamala Harris once again becomes the tie-breaker.

Sinema told The Republic that she plans to caucus with Democrats for committee seat purpose, like Sen. Bernie Sanders, I-Vt. Either way, nothing changes when it comes to passing legislation because of the 60-vote threshold.

However, budgetary matters and confirming federal judges requires only a simple majority, thus President Joe Biden can’t afford to lose any Democratic votes.

Sinema wants to make this tough for Democrats

Though she no longer has veto power, everything indicates she’ll make Democrats’ job difficult by scheming with Sen. Joe Manchin of West Virginia, as she has done in the past.

For two years, the pair of Democrats has hijacked Biden’s agenda by forcing major concessions that include changes and cuts to tax, health and climate legislation.

Republicans had expressed fear about the 51-49 split, particularly when it comes to confirming judges.

“It’ll be easier for Democrats to move forward with some of their nominees, particularly in the judiciary, and that makes it more difficult for us,” Sen. Mitt Romney, R-Utah, told The Wall Street Journal after Warnock’s victory.

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Sinema’s leaving the party changes the equation – again. In two years, Biden has confirmed nearly 90 of his judicial nominees. Former President Donald Trump placed 231 over four years, according to the Brookings Institution.

No matter what, Arizonans are stuck with Sinema for the next two years. Let’s hope she keeps working with Democrats and Republicans to get things done.

Make no mistake, though, ditching the Democratic Party has nothing to do with ugly partisan games but everything to do with Sinema’s opportunism.

Elvia Díaz is the editorial page editor for The Arizona Republic and azcentral.com. Follow her on Twitter: @elviadiaz1

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This article originally appeared on Arizona Republic: Sinema sticks it to Democrats as she prioritizes herself over Arizona