WASHINGTON – Senate hearings on Supreme Court nominee Neil Gorsuch ended Thursday on a confrontational note, with the body's top Democrat vowing a filibuster that could complicate Gorsuch's expected confirmation and ultimately upend the traditional approach to approving justices.

Senate Minority Leader Charles Schumer, D-N.Y., said he will vote "no" on President Donald Trump's nominee and asked other Democrats to join him in blocking an up-or-down vote on Gorsuch.

Under Senate rules, it requires 60 votes to overcome such an obstacle. Republicans eager to confirm Gorsuch before their Easter recess — and before the court concludes hearing the current term of cases next month — have only 52 senators.

Republicans have vowed Gorsuch will be confirmed even if it means overhauling the way justices have long been approved. Traditionally, senators can force the Senate to muster a supermajority just to bring up the nomination of a Supreme Court justice. If that is reached, the confirmation requires a simple majority.

In a speech on the Senate floor, Schumer said: "If this nominee cannot earn 60 votes — a bar met by each of President Obama's nominees and George Bush's last two nominees — the answer isn't to change the rules. It's to change the nominee."

The Democrats' liberal base has been pressuring senators to block Trump's nominees across the government.

But Schumer stopped short of saying that his entire Democratic caucus would join him in opposition to Gorsuch, leaving space for some Democrats to find ways to work with Republicans.

Democrats may not have the votes to block Gorsuch, 49, who has been on the Denver-based U.S. Court of Appeals for the last decade and was nominated to fill the Supreme Court seat left vacant since Justice Antonin Scalia died unexpectedly in February 2016.

Several Democrats, especially those facing upcoming re-election battles in states that Trump won, face opposition from conservative organizations bankrolling a multimillion-dollar ad campaign designed to bolster Gorsuch.

There are also competing views among Democrats about whether to filibuster Gorsuch's nomination — which could provoke the Republican majority to rewrite the rules — or instead avoid confrontation and preserve the filibuster threat for the future.

Retaining the filibuster could force Trump to select a moderate nominee if in the coming years he gets a chance to replace a second Supreme Court justice.

Among recent Supreme Court nominees the 60-vote threshold has not caused a problem. President Barack Obama's choices of Sonia Sotomayor and Elena Kagan each received more than 60 votes.

Samuel Alito Jr., chosen by President George W. Bush, was confirmed 58-42 in 2006, but 72 senators voted to defeat a possible filibuster and allow his confirmation vote to go forward. Only Alito — among the last 16 Supreme Court nominees — was forced to clear the supermajority hurdle to break a filibuster.

In announcing his confrontational approach, Schumer said that Gorsuch "was unable to sufficiently convince me that he'd be an independent check" on Trump. Schumer said later that the judge is "not a neutral legal mind but someone with a deep-seated conservative ideology," hand-picked for Trump by conservative legal groups.

Thomas Goldstein, a Supreme Court practitioner and co-founder of SCOTUSblog, said that Democrats on the Senate Judiciary Committee did not present a compelling case that Gorsuch was either an illegitimate nominee or that he was outside the conservative mainstream.

"None of the Democrats set the table" for a filibuster, Goldstein said.

He speculated that one option for some Democrats would be to allow an up-or-down vote, and then to vote against confirmation.

Sens. Thomas Carper, D-Del., Robert Casey Jr., D-Pa., and Ron Wyden, D-Ore., also announced Thursday that they would filibuster Gorsuch. Casey is one of 10 Democratic senators running next year in a state that Trump won.

The Judicial Crisis Network, which is spending at least $10 million on television ads to persuade Democratic senators to support Gorsuch, called Casey and other Democrats opposing Gorsuch "totally unreasonable" because "they will obstruct anyone who does not promise to rubber stamp their political agenda from the bench."

Senior Republicans have vowed that Gorsuch will be confirmed no matter what — a veiled threat to Democrats that they might use the so-called nuclear option to change the way senators confirm Supreme Court justices.

"If Judge Gorsuch can't achieve 60 votes in the Senate, could any judge appointed by a Republican president be approved with 60 or more votes in the Senate?" Senate Majority Leader Mitch McConnell, R-Ky., said.

Much of the Democratic resistance to Gorsuch centers on the GOP's decision last year to block a vote on Judge Merrick Garland, Obama's choice to replace Scalia.

But moderate Democrats have said they are hoping that the two parties can come to an agreement that leads to Gorsuch's confirmation and the preservation of current Senate traditions.