 -- The Senate’s top Democrat promised to deal a critical blow to the confirmation process of President Donald Trump’s nominee to the Supreme Court, Judge Neil Gorsuch, saying Democrats will invoke a filibuster, forcing Republicans to garner at least 60 votes to end debate in the Senate before he can be confirmed.

“After careful deliberation, I have concluded that I cannot support Judge Neil Gorsuch’s nomination to the Supreme Court,” Sen. Chuck Schumer, D-N.Y., said Thursday. “His nomination will have a cloture vote. He will have to earn 60 votes for confirmation.”

Democrats have threatened to force any of Trump’s Supreme Court nominees to clear procedural hurdles since last year. But Republicans have vowed that Gorsuch will be confirmed no matter what, even if it means controversial changes to Senate rules.

Throughout his confirmation hearing, Democratic members of the Senate Judiciary Committee repeatedly hit Gorsuch for his refusal to comment on his personal philosophies behind controversial rulings he delivered as a federal judge on the 10th Circuit.

“Judge Gorsuch was unable to sufficiently convince me that he’d be an independent check on a president who has shown almost no restraint from executive overreach,” Schumer said. “Second, he was unable to convince me that he would be a mainstream justice who could rule free from the biases of politics and ideology.

“My vote will be no, and I urge my colleagues to do the same,” he added.

But Republicans have the option of going nuclear, or changing the long-standing precedent for confirmation of presidential nominees and reducing the minimum number of votes required from 60 to a simple majority of 51.

Under Senate rules, three-fifths of senators are required to vote in favor of ending debate, or for cloture. But in 2013, Senate Democrats employed a series of procedural maneuvers to change that requirement to a simple majority, or 51 votes, for all Cabinet-level and judicial nominations, except for those to the Supreme Court. The elimination of the three-fifths threshold became known as the nuclear option.

Facing a confirmation fight over a judge for whom Democrats have pledged to require at least 60 votes — votes Republicans might not have — GOP senators are considering changing the threshold for approving Supreme Court nominees to 51 votes.

“To my Republican friends who think that if Judge Gorsuch fails to reach 60 votes, we ought to change the rules, I say, if this nominee cannot earn 60 votes, a bar met by each of President [Barack] Obama’s nominees and President [George W.] Bush’s last two nominees, the answer isn’t to change the rules, it’s to change the nominee,” Schumer said.

Today, White House press secretary Sean Spicer called on Schumer to back down from the threat to filibuster Gorsuch.

“We call on Democrats to abandon this attempt to block Judge Gorsuch from receiving a fair up or down vote that he and the American people have voted for,” Spicer said.

ABC News’ Lissette Rodriguez and Ali Rogin contributed to this report.