Senate majority leader Chuck Schumer, D-N.Y., previously defended the filibuster in 2005 despite threatening to nix the rule in recent weeks.
Schumer 16 years ago fought in favor of the long-standing Senate procedural rule, which has come under scrutiny a number of times throughout the past 20 years, that allows lawmakers to block legislation through unlimited debate unless 60 members move to a vote.
"We are on the precipice of a crisis. A constitutional crisis. The checks and balances which have been at the core of this republic are about to be evaporated by the nuclear option," Schumer said, referencing an option to eliminate the filibuster, during a 2005 speech. "The checks and balances which say that if you get 51% of the vote, you don’t get your way 100% of the time."
FLASHBACK: OBAMA DEFENDED FILIBUSTER IN 2005, NOW CALLS IT 'JIM CROW RELIC'
He added that discussion of the "nuclear option" was "almost a temper tantrum by those on the hard, hard right," who "want … their way every single time."
"They will change the rules, break the rules, misread the Constitution so that they will get their way," he said. "That ... is what we call abuse of power."
Several Democratic lawmakers have signaled they would support an effort to remove the 60-vote threshold required to pass legislation, even as Republicans warn of total legislative gridlock if they proceed.
Schumer argued Thursday that Democrats were justified in filibustering legislation in the GOP-controlled Senate during the last session of Congress because Republicans refused to engage in bipartisan negotiations.
When asked why the Democrats once used the filibuster to similar effect, Schumer blamed tactics employed by Senate Minority Leader Mitch McConnell, R-Ky., when the Republicans held the majority.
"The big difference is that we were always willing to negotiate in a bipartisan way," Schumer said at a press conference. "Mitch McConnell isn’t. The bills he puts on the floor, even when he calls them bipartisan, aren’t, like the first CARES bill, like the policing bill. There’s no discussion, no discussion."
Schumer said he was "encouraging my colleagues to sit down with Republicans" to find common ground on legislation. However, the majority leader warned that he would be open to changing filibuster rules if bipartisan talks failed to yield progress.
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McConnell has warned of a "scorched-earth Senate" if Democrats attempt to end use of the filibuster. In a floor speech earlier this week, the Kentucky senator argued that Democrats used the same tactic to detail a GOP-backed police reform bill following the death of George Floyd last May.
Fox News' Thomas Barrabi contributed to this report.