“This is a stolen seat. This is the first time a Senate majority has stolen a seat,” Sen. Jeff Merkley said in an interview. | AP Photo Senate Dems will filibuster Trump’s Supreme Court nominee It will be only the second time in modern history that the Senate has mounted a filibuster against a nominee.

Senate Democrats are going to try to bring down Donald Trump's Supreme Court pick no matter who the president chooses to fill the current vacancy.

With Trump prepared to announce his nominee on Tuesday evening, Sen. Jeff Merkley (D-Ore.) said in an interview on Monday morning that he will filibuster any pick that is not Merrick Garland and that the vast majority of his caucus will oppose Trump’s nomination. That means Trump's nominee will need 60 votes to be confirmed by the Senate.

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“This is a stolen seat. This is the first time a Senate majority has stolen a seat,” Merkley said in an interview. “We will use every lever in our power to stop this.”

It’s a move that will prompt a massive partisan battle over Trump’s nominee and could lead to an unraveling of the Senate rules if Merkley is able to get 41 Democrats to join him in a filibuster. Sen. Amy Klobuchar (D-Minn.) also reminded her Twitter followers on Sunday night that Supreme Court nominees can still be blocked by the Senate minority, unlike all other executive and judicial nominees.

Any senator can object to swift approval of a nominee and require a supermajority. Asked directly whether he would do that, Merkley replied: “I will definitely object to a simple majority” vote.

Merkley's party leader, Sen. Chuck Schumer of New York, has said he will fight "tooth and nail" any nominee who isn't "mainstream."

It would be only the second time in modern history that the Senate has mounted a filibuster against a nominee. Democrats, including then-Sen. Barack Obama, tried to block the confirmation of Samuel Alito in 2006 but failed. Obama’s Supreme Court nominees each received more than 60 votes, but Republicans did not require a supermajority or the procedural vote that Merkley will demand.

Republicans immediately dinged Merkley as a hypocrite for being a leading advocate of changing the Senate rules four years ago.

"When Democrats were in the majority, Sen. Merkley wanted to end filibusters. But I guess he only meant when Democrats are in the majority and in control of the White House," said Don Stewart, a spokesman for Senate Majority Leader Mitch McConnell (R-Ky.).

The Democratic stance dashes McConnell's hopes to return to the tradition of not filibustering Supreme Court nominees. In an interview with POLITICO on Friday, McConnell said the “practice was that you didn’t do it even though the tool is in the toolbox.”

“There are a lot of tools in there. Until Bush 43, the filibuster tool was always there. But it wasn’t done,” McConnell said. “Two good examples: There was no filibuster against [Robert] Bork and, of course, the most controversial Supreme Court nomination ever was Clarence Thomas. Democrats were in the majority; he was approved 52-48.”

But McConnell blocked Garland from even having a hearing for nearly a year during the end of Obama’s presidency, and Democrats have not forgotten his unprecedented blockade. They’ve been lining up party-line votes against some of Trump’s Cabinet nominees — and now, Democrats like Merkley are laying the groundwork to halt the only nominee that they have ultimate leverage over.

“A very large number of my colleagues will be opposed,” Merkley said.

POLITICO has reported the leading contenders for the nomination are Judge Thomas Hardiman of the 3rd U.S. Circuit Court of Appeals and Judge Neil Gorsuch of the 10th U.S. Circuit Court of Appeals. They were confirmed to appeals courts without a dissenting vote, though Democrats are sure to treat them more harshly after Garland's nomination stalled for months.

McConnell is loath to change the rules of the Senate to allow confirmation of Supreme Court nominees by a simple majority but has not said explicitly what he would do if Democrats block Trump’s nominee. The Senate rules can be changed by a simple majority using the so-called "nuclear option" — last invoked by former Majority Leader Harry Reid (D-Nev.) to ease the confirmation of Obama's judicial and executive nominees.

The Kentucky Republican told POLITICO that it’s up to Democrats where the Senate rules go — but also guaranteed Trump’s nominee will be confirmed, an implicit threat that if at least eight Democrats don’t get on board, there could be a unilateral rules change.

“We’re going to get this nominee confirmed. I hope he or she will be confirmed based upon the completely outstanding credentials that we’re going to see,” McConnell said. The nominee "hopefully will be treated the way such a nominee would have been treated as recently as Bush 43.”

Trump has made clear he wants McConnell to go nuclear if Merkley and other liberal Democrats are successful in blocking his high court pick's nomination.