FILE - In this March 22, 2017 file photo, Supreme Court Justice nominee Neil Gorsuch testifies on Capitol Hill in Washington before the Senate Judiciary Committee. Senate Democratic opposition to President Donald Trump's Supreme Court nominee swelled Friday, March 31, 2017, as Democrats neared the numbers needed for a filibuster, setting up a showdown with Republicans who have the votes to confirm Neil Gorsuch. (AP Photo/Susan Walsh, File)
FILE - In this March 22, 2017 file photo, Supreme Court Justice nominee Neil Gorsuch testifies on Capitol Hill in Washington before the Senate Judiciary Committee. Senate Democratic opposition to President Donald Trump's Supreme Court nominee swelled Friday, March 31, 2017, as Democrats neared the numbers needed for a filibuster, setting up a showdown with Republicans who have the votes to confirm Neil Gorsuch. (AP Photo/Susan Walsh, File) Credit: ap photograph

Washington — One of Senate’s most serious jobs — confirming the president’s choice for a lifetime appointment to the Supreme Court — has devolved into a game of political chicken.

Senators are heading toward an institution-defining showdown next week as Democrats promise to try to block President Donald Trump’s nominee, Judge Neil M. Gorsuch, with a filibuster, a rarely seen maneuver for Supreme Court appointments.

Republicans are threatening to respond by changing long-standing Senate rules to circumvent the 60 votes that would be needed to overcome a filibuster. Instead they would allow confirmation with a simple majority.

The outcome has the potential to not only shape the future of the Supreme Court — which has been without a full bench since the sudden death of Justice Antonin Scalia last year — it also could crush one final vestige of bipartisanship in the Senate, altering the upper chamber for years to come.

“It churns our stomach,” said Sen. Mike Rounds, R-S.D., as senators weighed their options this week.

Pressed if they were really ready to invoke the so-called “nuclear option” to ensure Gorsuch is confirmed, many Republican senators this week demurred.

“Can I answer you that in a couple days?” said Sen. Bill Cassidy, R-La.

But others — notably seasoned institutionalists, including Sen. Orrin Hatch, of Utah, the senior-most Senate Republican — appear ready to overhaul the rules for Trump.

“Judge Gorsuch is going to be confirmed. By any means necessary,” Hatch said in a statement.

The battle over the Supreme Court seat was always expected to be a partisan affair in today’s heated political climate. But the polemics intensified after the Republican majority denied President Barack Obama’s nominee, Judge Merrick Garland, a confirmation hearing ahead of last year’s presidential election.

Now the Gorsuch nomination is being viewed as a must-win for Republicans, as Trump’s first 100 days have faltered. For Democrats it has become a proxy for a broader opposition to Trump’s administration and the Republican agenda.

Senate Minority Leader Charles E. Schumer, D-N.Y., is trying to hold the Democratic minority together to deny Republicans the 60 votes needed to advance Gorsuch past a filibuster.

Republicans, with their 52-seat majority, must peel off eight Democrats to overcome the filibuster.

All four Twin State senators have said they will vote against Gorsuch’s confirmation.

If Republicans are unable to overcome the filibuster, Senate Majority Leader Mitch McConnell, R-Ky., is expected to do as former Senate Majority Leader Harry Reid, D-Nev., did in 2013, when he used the Democratic majority to change Senate rules to allow a simple majority vote for other types of judicial nominations. Reid said the move was needed to overcome Republican filibusters.

“Once they let the genie out, it’s not going back,” Rounds said. “It never should have been done, but now that is the precedent in the United States Senate.”

Neither McConnell nor Schumer will say, exactly, how many senators they have on their side. Each suggests the other is bluffing.

McConnell has repeatedly promised that Gorsuch will be confirmed on April 7, before the two-week spring recess. “I’m confident he’ll be confirmed,” he said.

Schumer was equally certain. “It’s going to be a real uphill climb for him to get those 60 votes,” he said.

The test vote is expected next week.

Republicans went into the court fight thinking their task would be easy enough. Gorsuch, the affable Colorado appellate judge, was viewed as a conservative who might be able to attract some Democratic votes.

Republicans also expected the politics would be on their side. Democrats from the red states that Trump won, particularly those up for re-election in 2018, they reasoned, would be more interested in bucking their party than crossing the new president.

Sen. Claire McCaskill, a Democrat up for re-election in red-state Missouri, said late Friday that she will not support the nomination and will join a Democratic effort to block his confirmation vote.

Since Trump nominated Gorsuch, the dynamics have dramatically shifted.

Trump’s approval rating continues to nosedive amid the FBI probe into possible collusion between his campaign and Russia, and his own missteps over the botched travel ban and failed repeal of the Affordable Care Act, known as Obamacare.

At the same time, Democrats quickly shifted from being chastened by their November electoral loss to emboldened — even pressured — by the sudden outpouring of liberal resistance to Trump’s presidency, particularly street protests that erupted in the weeks after the inauguration.

“The base really cares about this, and I think people understand that going along with someone as extreme as Neil Gorsuch is not just bad for the country, it’s bad politics,” said Drew Courtney, spokesman at the liberal advocacy group People for the American Way. “This is the first opportunity for senators to show they will stand and fight. Nothing will do more to dampen enthusiasm than for Democrats to fold on this.”