WASHINGTON — Democrats have secured the votes to block President Donald Trump’s Supreme Court nominee under current rules, putting the Senate on a partisan collision course over confirming Neil Gorsuch to a lifetime appointment that could reverberate for decades.

Debate over the 49-year-old appellate judge gets under way in the full Senate on Tuesday, with Republicans and Democrats bitterly divided over the next steps.

While Democrats have the votes for a filibuster, Majority Leader Mitch McConnell is ready to lead the GOP in a unilateral change in a Senate floor procedure so significant that it has been dubbed the “nuclear option.” The tactic if invoked would lower the confirmation threshold to a filibuster-proof simple majority of 51 votes in the 100-member Senate rather than the 60 votes currently needed to stop delaying tactics by opponents.

The likelihood of more partisan wrangling left veteran GOP senators frustrated — and hoping that Democrats would relent in their opposition to the Colorado jurist.

The nuclear option would be “damaging to the Senate, damaging to them and damaging to the country. Maybe a light will come on somewhere,” said Sen. Lamar Alexander, a Tennessee Republican.

After hours of debate Monday, the Judiciary Committee voted 11-9, along party lines, to send Gorsuch’s nomination to the full Senate, where McConnell, R-Ky., has vowed he will be confirmed on Friday.

Sen. Chris Coons of Delaware became the key 41st vote for the Democrats, declaring during a committee debate that Gorsuch’s conservative record showed an activist approach to the law, often in favor of business interests, and that he evaded questions during his confirmation hearings. Coons also said that Republicans’ treatment of former President Barack Obama’s Supreme Court nominee, Merrick Garland, left lasting scars after they denied him so much as a hearing following the death of Justice Antonin Scalia early last year.

“We are at a historic moment in the history of the United States Senate” due to actions by both parties, Coons said. “We have eroded the process for reaching agreement and dishonored our long traditions of acting above partisanship.”

The long-term consequences of the coming confrontation could be profound, as the rules change Republicans intend to enact would apply to future Supreme Court nominees as well, allowing them to be voted onto the court without any input from the minority party. And though predicting a justice’s votes can be difficult, confirmation of the 49-year-old Gorsuch is expected to restore the conservative majority that existed while Scalia was alive and that majority could be expanded in coming decades if Republicans remain in control of the process. Some of the more liberal justices are among the oldest on the court, so more court openings could pop up.