Updated at 4:18 p.m. ET

Senate Democrats said Monday they have the required 41 votes to sustain a filibuster against Supreme Court nominee Neil Gorsuch’s confirmation.

Assuming none of the 41 senators change their minds before the final vote later this week, the Senate’s Republican majority will almost certainly invoke the so-called “nuclear option” to rewrite the legislative chamber’s rules and place Gorsuch on the nation’s highest court.

Democrats crossed the fateful threshold during a Senate Judiciary Committee hearing Monday, where senators debated Gorsuch’s nomination ahead of a committee vote. Delaware Senator Chris Coons followed Democratic colleagues Dianne Feinstein and Patrick Leahy in announcing his opposition to letting the nomination advance, becoming the key 41st senator to back the filibuster. “I am not ready to end debate on this issue, so I will be voting against cloture,” Coons told the committee, referring to the formal procedural mechanism to end a filibuster.

Passing legislation or confirming a president’s nominees theoretically requires a simple majority of 50 votes in the Senate. But senators can—and increasingly do—use filibusters held on the floor of the Senate to delay and block final votes. Overcoming a filibuster under current Senate rules requires the assent of 60 senators, making it a potent tool for the minority party to check the majority’s ambitions.

But that threshold can be eliminated by invoking the nuclear option, under which the Senate rewrites its own standing rules in a simple-majority vote. The procedural tactic earned its colloquial name from its sweeping power: Senate Democrats under former Majority Leader Harry Reid invoked it in 2013 to eliminate the 60-vote threshold for virtually all presidential appointments, citing the Republican minority’s unprecedented efforts to block Obama administration nominees. Democrats left the filibuster intact for Supreme Court nominees, however, leading to the current standoff.

Senate Republican leaders, including Majority Leader Mitch McConnell, have already signaled they would go nuclear to place Gorsuch on the Court. If confirmed, the 49-year-old federal appellate judge from Colorado would fill the record 14-month vacancy left by the death of Justice Antonin Scalia in February 2016. His unexpected death gave Barack Obama his third opportunity to nominate a justice to the Supreme Court. In March, he nominated Merrick Garland, the well-respected chief judge of the D.C. Circuit Court of Appeals and a relative moderate among the likely Democratic choices for the Court.

Within an hour of Scalia’s death, however, McConnell vowed to not confirm any of Obama’s nominees until after the election later that year. While McConnell cited the then-upcoming presidential contest as a reason not to confirm any Supreme Court nominee, Democrats attacked the unprecedented refusal as nakedly partisan. Confirming any Obama nominee would’ve given the Court’s liberal wing its first five-justice majority since the 1960s—a major shift in the high court’s ideological balance after almost a half-century of conservative dominance. President Trump’s victory in November foreclosed that shift for the immediate future, vindicating McConnell’s blockade.

Contentious battles over Supreme Court nominees have been uncommon historically, but not unheard of. Lyndon Johnson nominated Justice Abe Fortas to replace Earl Warren as the Court’s chief justice in 1968, for example, only to see the nomination flounder amid a bipartisan filibuster over ethics concerns and the Warren Court’s ideological leanings. But where such clashes were once rare, partisan confirmation battles have increasingly become more typical over the past three decades.

At a glance, the recent record might suggest otherwise. Senators approved Scalia, Anthony Kennedy, and Ruth Bader Ginsburg by unanimous or near-unanimous margins between 1986 and 1993 despite their broad ideological differences. But there were acrimonious fights, too. The Democratic-led Senate rejected Ronald Reagan nominee Robert Bork, a prominent legal thinker on the right, in a heated showdown over his philosophical stances in 1987—a defeat conservatives still invoke today. Clarence Thomas, the Court’s second black justice, described his confirmation process in 1991 as a “high-tech lynching” after sexual-harassment allegations nearly derailed his nomination.

The trend accelerated after the Supreme Court resolved the 2000 presidential election, its sharply divided 5-4 vote underscoring how the Court’s ideological balance could change the country. Three of the four justices nominated by George W. Bush and Obama were confirmed with more than 30 senators from the opposing party voting no. Democrats questioned Samuel Alito, who replaced Sandra Day O’Connor, about his views on abortion at length, while Republicans criticized Sonia Sotomayor for once saying a “wise Latina woman” could sometimes make better judicial decisions than a white man without her experiences. Both nominees were confirmed, but the parameters for future warfare were staked out.

Those partisan struggles will likely reach their logical conclusion with the filibuster’s elimination for Supreme Court nominees. Longtime senators often express pride in the Senate’s history as a more collegial and deliberative legislative body than the strongly partisan House. That tradition, at least where the nation’s highest court is concerned, appears to be coming to a close this week.