WASHINGTON — (CNN) One empty seat on the Supreme Court has changed everything.

Washington is adjusting to a new political reality after the sudden death of Justice Antonin Scalia, which left a turbulent White House race transformed, a lame-duck president back at the center of the political storm and Senate Republican leaders juggling an electoral hand grenade.

After the shock of Scalia’s passing and the swift eruption of a bitter partisan feud over his replacement, President Barack Obama and his GOP adversaries will this week begin digging deep for a showdown that will define an already tumultuous political year.

Obama has upped the ante by making clear that he will defy Republican leaders and presidential candidates who warn he should leave the momentous task of nominating a new justice, who could tip the balance of the Court to liberals, to a new administration.

But the White House is also signaling that the President, who is in California for a summit of southeast Asian leaders, will not immediately seek to jam the Senate, which is on recess for the next week, with a Supreme Court nominee.

“We don’t expect the President to rush this through this week but instead will do so in due time once the Senate returns from their recess,” White House spokesman Eric Schultz said Sunday. “At that point, we expect the Senate to consider that nominee, consistent with their responsibilities laid out in the United States Constitution.”

That position ensures a titanic fight over Scalia’s replacement, placing Obama on a collision course with Republicans while thickening the plot of an election that now leaves the White House, the Senate and the nation’s top court up for grabs.

GOP presidential candidates are leading the charge in the battle over a replacement for Scalia, a beloved icon for conservatives who was found dead at the age of 79 at a resort in West Texas on Saturday. They are warning that since an appointment could remake the court for a generation as key legal battles over abortion rights, affirmative action and campaign finance loom, it should be put off until next year.

“This is for the people to decide,” Texas Sen. Ted Cruz said at a rally in South Carolina on Monday. “I intend to make 2016 a referendum on the U.S. Supreme Court.”

Capitol Hill battle

Republican Senate Majority Leader Mitch McConnell has already warned Obama not to try to fill the vacancy on the Court, saying it should be up to a new president to weigh in once voters have spoken in November.

McConnell must navigate a treacherous political moment and decide whether a Republican maneuver to block a confirmation process could benefit his party at the polls or risk driving up Democratic turnout in November and put his grip on the Senate at risk.

Democrats have reacted furiously to the Republican gambit, arguing that the Constitution vests the President, who does not leave office until next January, with a duty to name a new Supreme Court nominee.

“The fact is, when you elect a president, you have to assume a Supreme Court vacancy, he is going to make the nomination,” said Patrick Leahy, the top Democrat on the Senate Judiciary Committee. “It would be a sheer dereliction of duty for the Senate not to have a hearing, not to have a vote,” Leahy said Sunday on CNN’s “State of the Union.”

Leahy implicitly warned that the fate of the Court would be an issue certain to fire up the Democratic base in November’s elections if an Obama nominee is left in limbo.

“If the Republican leadership refuses to even hold a hearing, I think that is going to guarantee they’re going to lose control of the Senate,” Leahy said.

Pressure on Republicans

Obama could decide to build political pressure on Republicans, either by nominating a judge who has already been confirmed by the Senate for a lower-ranking post — for instance, Judge Sri Srinavasan on the U.S. Court of Appeals for the District of Columbia Circuit — or a more moderate nominee than the GOP expects, to make an implicit point that his choice is not controversial.

But Republicans, who control the Senate, have the discretion not to bring up any nominee in the chamber for consideration — meaning a huge political fight is likely to ensue.

Democratic presidential candidates, like their Republican counterparts, wasted no time in leveraging the death of Scalia into a campaign rallying call.

Hillary Clinton, at a campaign stop in Denver Saturday night, said, “Barack Obama is president of the United States until January 20, 2017. That is a fact, my friends, whether the Republicans like it or not.”

The sudden political crisis also put one group of Republicans — swing-state senators whose seats could dictate whether the GOP can hang on to the chamber in November — in a difficult position.

Privately, senior Democratic officials told CNN that there’s little chance of Obama’s nominee winning confirmation unless these endangered GOPers break ranks.

On Sunday, several vulnerable incumbents, including Pat Toomey of Pennsylvania and Mark Kirk of Illinois, would not say if they wanted the Senate to deny Obama’s nominee a vote.

Sen. Joe Manchin, a centrist Democrat from West Virginia, who often votes with Republicans, wants the Senate to act on a nominee when the President puts one forward, an aide to the senator told CNN.

But several others made clear they stood with Republican leaders who believe that the issue could invigorate conservative turnout in November.

“I strongly agree that the American people should decide the future direction of the Supreme Court by their votes for president and the majority party in the U.S. Senate,” Sen. Ron Johnson of Wisconsin, a vulnerable incumbent, said in an email to CNN.

And in a statement, Sen. Kelly Ayotte, a New Hampshire Republican facing a competitive reelection fight in 2016, said the Senate should not confirm a Supreme Court nominee until a new president is elected.

“We’re in the midst of a consequential presidential election year,” Ayotte said, “and Americans deserve an opportunity to weigh in given the significant implications this nomination could have for the Supreme Court and our country for decades to come.”

Sen. Rob Portman, an Ohio Republican up for re-election this year, said Monday he also thought the future president should nominate Scalia’s replacement.

“Whether the next president is a Republican or Democrat, I will judge any nominee on the merits, as I always have,” Portman said in a statement.

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