Arizona Democrat Rep. Ruben Gallego is offering heavy criticism of Sen. Kyrsten Sinema after she announced Friday that she was leaving the Democratic Party.

In a statement issued shortly after it was made public that Sinema was leaving the Democratic Party to become an independent, Gallego, who could pose an election challenge to Sinema, accused the senator of "putting her own interests" ahead of those most pertinent to Arizona residents.

"Last month, the voters of Arizona made their voices heard loud and clear — they want leaders who put the people of Arizona first," Gallego said. "We need senators who will put Arizonans ahead of big drug companies and Wall Street bankers. Whether in the Marine Corps or in Congress, I have never backed down from fighting for Arizonans. And at a time when our nation needs leadership most, Arizona deserves a voice that won’t back down in the face of struggle."

"Unfortunately, Senator Sinema is once again putting her own interests ahead of getting things done for Arizonans," he added.

ARIZONA SEN. KYRSTEN SINEMA LEAVES DEMOCRATIC PARTY, REGISTERS AS INDEPENDENT

Ruben Gallego, Kyrsten Sinema

Arizona Democrat Rep. Ruben Gallego, left, and Arizona Democratic Sen. Kyrsten Sinema. (Anna Moneymaker, Al Drago/Bloomberg via Getty Images)

Sinema, in a Friday op-ed in the Arizona Republic, cited increasingly partisan interests and radicalization of both political parties as the reason for her departure.

"Americans are told that we have only two choices — Democrat or Republican — and that we must subscribe wholesale to policy views the parties hold, views that have been pulled further and further toward the extremes," Sinema wrote in the op-ed.

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"Most Arizonans believe this is a false choice, and when I ran for the U.S. House and the Senate, I promised Arizonans something different," she continued. "I pledged to be independent and work with anyone to achieve lasting results. I committed I would not demonize people I disagreed with, engage in name-calling, or get distracted by political drama."

Sinema went on to accuse mainstream political parties in the U.S. of worrying more about blocking each other out than the well-being of their constituents.

Arizona Sen. Kyrsten Sinema speaks on Capitol Hill

Sen. Kyrsten Sinema, D-Ariz., speaks at a news conference after the Senate passed the Respect for Marriage Act at the Capitol Building on Nov. 29, 2022, in Washington, D.C. (Anna Moneymaker/Getty Images`)

The senator has been the target of extensive intra-party mudslinging for not falling in line with the rest of her party on key issues — most notably, refusing to abolish the filibuster.

"When politicians are more focused on denying the opposition party a victory than they are on improving Americans’ lives, the people who lose are everyday Americans," Sinema wrote in the op-ed.

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She added, "That’s why I have joined the growing numbers of Arizonans who reject party politics by declaring my independence from the broken partisan system in Washington. I registered as an Arizona independent. "

Fox News' Timothy H.J. Nerozzi and Chad Pergram contributed to this report.