"It's going to depend on how obstreperous they become," the former vice president said of Senate Republicans who might filibuster legislation championed by a potential Biden administration. “But I think you’re going to just have to take a look at it."

As recently as February 2020, Biden opposed ending the filibuster. The openness to change from Biden comes as he has clinched the Democratic nomination and is attempting to appeal to skeptical left-wing voters.

“I do think we’ve reached a point, a real inflection in American history. And I don’t believe it’s unlike what Roosevelt was met with,” Biden told reporters on Monday. “I think we have an opportunity to make some really systemic change.”

The filibuster refers to efforts from senators to block legislation and obstruct a vote from taking place by engaging in endless debate. Under current Senate rules, 60 votes are needed to invoke cloture, ending debate and sending the proposed legislation to a vote.

Southern segregationist senators used the filibuster to attempt to block multiple civil rights laws in the 1950s and 1960s, and Democrats decried Senate Republicans for filibustering during former President Barack Obama’s administration.

Biden’s comments come amid a shift in messaging from traditionally centrist Democrats, who now are no longer ruling out aggressive action to pass legislation. Most prominently, Biden ally Sen. Chris Coons (D-Del.) told POLITICO in June that he would not rule out banning the filibuster.

“I will not stand idly by for four years and watch the Biden administration's initiatives blocked at every turn,” Coons said. “I am gonna try really hard to find a path forward that doesn't require removing what's left of the structural guardrails, but if there's a Biden administration, it will be inheriting a mess, at home and abroad. It requires urgent and effective action.”

In 2017, Coons spearheaded a letter to support the filibuster and block measures from fellow Democrats to eliminate it.

Biden may have an unlikely ally in his quest to end the filibuster: the man he is trying to beat in November. In September 2017, President Donald Trump tweeted his approval for ending the fillibuster.

“With the ridiculous Filibuster Rule in the Senate, Republicans need 60 votes to pass legislation, rather than 51,” Trump wrote. “Can't get votes, END NOW!”

But despite the president's calls for an end to the filibuster, Senate Majority Leader Mitch McConnell has refused to do away with teh 60-vote threshold for legislation.