Sinema’s move sparked an immediate backlash from Democrats, who took to Twitter to express their anger and frustration with the newly-minted Independent.

The Arizona Democratic Party ripped Sinema for declining to scrap the Senate’s legislative filibuster to pass election reform legislation and for opposing increases in corporate tax rates, saying she was “leaving Arizonans behind.” …

Progressive Rep. Ruben Gallego (D-Ariz.), seen by many as a potential challenger to Sinema in 2024, accused her of “once again putting her own interests ahead of getting things done for Arizonans.”

“We need Senators who will put Arizonans ahead of big drug companies and Wall Street bankers,” Gallego said. “Whether in the Marine Corps or in Congress, I have never backed down from fighting for Arizonans. And at a time when out nation needs leadership the most, Arizona deserves a voice that won’t back down in the face of struggle.”

“She’s not driven by ideology,” tweeted Melanie D’Arrigo, a former Democratic congressional candidate from New York. “She’s driven by which corporations and lobbyists are giving her the most money — which makes her an elected mercenary, not an elected representative of the people.”

Democratic strategist Adam Parkhomenko was even less diplomatic, tweeting: “I see Kyrsten Sinema is still great at being the f—ing worst.”

[Gallego was planning a primary challenge to Sinema. Her disaffiliation changes the ground for him, which is why he’s so angry. I have more on that in a main-blog post. — Ed]