Sen. Kyrsten Sinema Monday doubled down on her defense of the Senate’s legislative filibuster, declaring in a Washington Post op-ed that it is important to stop "repeated radical reversals" of federal law.

Sinema, D-Ariz., and Sen. Joe Manchin, D-W.Va., have been the two most vocal Democrats in the chamber defending the 60-vote threshold for legislation, often attracting the ire of their more liberal colleagues. And Sinema took a page from Manchin’s playbook Monday by laying out her case for the Senate’s controversial minority protection in an opinion piece.

"To those who want to eliminate the legislative filibuster to pass the For the People Act (voting-rights legislation I support and have co-sponsored), I would ask: Would it be good for our country if we did, only to see that legislation rescinded a few years from now and replaced by a nationwide voter-ID law or restrictions on voting by mail in federal elections, over the objections of the minority?" Sinema wrote in The Post.

"This question is less about the immediate results from any of these Democratic or Republican goals," she continued. "[I]t is the likelihood of repeated radical reversals in federal policy, cementing uncertainty, deepening divisions and further eroding Americans’ confidence in our government."

Sen. Kyrsten Sinema, D-Ariz., heads back to a bipartisan meeting on infrastructure in the basement of the U.S. Capitol building after the original talks fell through with the White House on June 8, 2021, in Washington, D.C. Sinema wrote in the Washington Poston  Monday that she supports the 60-vote filibuster threshold for bills in the Senate. (Samuel Corum/Getty Images)

Sen. Kyrsten Sinema, D-Ariz., heads back to a bipartisan meeting on infrastructure in the basement of the U.S. Capitol building after the original talks fell through with the White House on June 8, 2021, in Washington, D.C. Sinema wrote in the Washington Poston  Monday that she supports the 60-vote filibuster threshold for bills in the Senate. (Samuel Corum/Getty Images)

MANCHIN ON FILIBUSTER: WV SENATOR DODGES QUESTIONS ON POTENTALLY LOWERING THRESHOLD TO 55

The majority of the Democrats in the Senate signed a 2017 letter led by Sens. Susan Collins, R-Maine, and Chris Coons, D-Del., asking Senate leaders to preserve the filibuster during the Trump presidency. 

But as the 2020 election approached, and especially since President Biden was sworn in earlier this year, many Democrats renounced or at least distanced themselves from that stance, including Coons. Now Manchin and Sinema are the only two staunch filibuster defenders among Senate Democrats, with a few other moderates and institutionalists who quietly support them.

Sinema notes in her op-ed that Democrats often used the filibuster to stop Republican-supported legislation during President Trump's tenure, when Republicans controlled the Senate. 

"Once in a majority, it is tempting to believe you will stay in the majority. But a Democratic Senate minority used the 60-vote threshold just last year to filibuster a police reform proposal and a covid-relief bill that many Democrats viewed as inadequate," Sinema wrote. "Those filibusters were mounted not as attempts to block progress, but to force continued negotiations toward better solutions."

DEMOCRATS DISTANCE THEMSELVES FROM PREVIOUS PRO-FILIBUSTER STANCE, CITING GOP OBSTRUCTION

Progressive Democrats, meanwhile, argue that the filibuster is racist and say eliminating it is necessary for Democrats to pass an agenda they deem critical to the country. 

"An archaic Senate rule cannot get in the way of protecting our democracy," Sen. Amy Klobuchar, D-Minn., tweeted over the weekend, before the Sinema op-ed. Klobuchar was notably one of the Democrats who supported the filibuster in 2017 when Republicans were in power.

"Filibuster supporters be like: we should let Republicans destroy democracy now because at some indeterminate time in the future they may try again," Rep. Mondaire Jones, D-N.Y., who is one of the loudest supporters of getting rid of the filibuster in Congress, tweeted Monday. 

Sinema's and Manchin's commitment to the filibuster throws a wrench into the plans of Democrats who'd hoped GOP opposition to S.1 and other Democrat-backed legislation the Senate will soon vote on would spur moderates to shun the filibuster and pass all of Biden's expansive agenda via simple majority. 

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Instead, S.1, an elections bill that would massively expand the role of the federal government in how states run their elections, will likely not even get the support of all 50 Democrats when Majority Leader Chuck Schumer, D-N.Y., brings it for a cloture vote Monday. Manchin, the only Democrat not to co-sponsor S.1, has said he won't vote for it.