U.S. Supreme Court Justice Antonin Scalia
© Darren Ornitz / Reuters
Republican lawmakers and presidential candidates hardened their positions on Sunday on blocking a move by President Barack Obama to fill the seat left by the late conservative Justice Antonin Scalia on the Supreme Court, a lifetime appointment that would help decide some of the most divisive issues facing Americans.

The next justice could tilt the balance of the nation's highest court, which was left with four conservatives and four liberals. The vacancy quickly became an issue in the 2016 presidential race.

"We ought to make the 2016 election a referendum on the Supreme Court," U.S. Senator and Republican presidential candidate Ted Cruz said on NBC's "Meet the Press."

The normally nine-justice court is set to decide this year its first major abortion case in nearly a decade, as well as cases on voting rights, affirmative action and immigration.

Scalia, 79, died on Saturday at a West Texas resort. The cause of death was a heart attack, Texas television station WFAA-TV reported on Sunday, citing a Texas county judge.

Obama, a Democrat, said on Saturday that he would nominate someone to fill the empty seat, setting up a battle with the Republican-controlled Senate, which must approve any nominee.

Republicans quickly vowed not to act on the vacancy until Obama's successor takes office next January. Senate Democratic leader Harry Reid said failure to act would be a "shameful abdication" of the Senate's constitutional duty.

Both sides claimed history was on their side.

Reid said it would be unprecedented to have a vacancy on the court for a year. In the modern era, the longest Supreme Court vacancy was 363 days after Abe Fortas resigned in May 1969.

Republicans cited 80 years of tradition in which no Supreme Court nominees were approved in presidential election years. In fact, Justice Anthony Kennedy was approved in 1988, after a bruising battle in which the Senate rejected President Ronald Reagan's first nominee, conservative Robert Bork.

Supreme Court nominations are rare, so neither side has much data to rely on in determining precedents. History is also an unreliable guide as the nomination process has become significantly more politicized in recent years.

Deep divisions

Ohio Governor John Kasich, a moderate among the Republicans vying for the White House, said the Senate should wait because a battle this year would only deepen divisions in the country.

"You know how polarized everything is," Kasich said on ABC's "This Week." "What I don't want to see is more fighting and more recrimination."

Democratic U.S. Senator Patrick Leahy warned that a delay could have consequences in November's election, when voters get to decide who fills one-third of the Senate's seats.

"If the Republican leadership refuses to even hold a hearing, I think that is going to guarantee they lose control of the Senate, because I don't think the American people will stand for that," he said on CNN's "State of the Union."

Democratic presidential candidate Bernie Sanders said the Constitution was clear. "The president makes the appointment, Senate confirms, let's get on with that business," the senator said on "Fox News Sunday."

Cruz, who sits on the Senate Judiciary Committee that takes the lead on Supreme Court nominees, said the vacancy left by Scalia makes the presidential election even more critical.

He warned that a justice chosen by Sanders or his Democratic presidential rival, Hillary Clinton, would mean the Second Amendment right to bear arms would be "written out" of the Constitution and abortion on demand would become the law of the land.

Cruz lumped Donald Trump in with the Democrats, saying the Republican front-runner's views were indistinguishable from theirs.

Republican Senator Marco Rubio, another White House rival, said he would want someone who echoed Scalia's "originalist" ideology that looks at the U.S. Constitution through the lens of its framers' 18th-century intentions.

"Does the person that we are nominating have a consistent and proven record of interpreting the Constitution as initially meant?" Rubio said.

Trump, appearing on NBC, was more direct when asked what he would want: "Someone just like Justice Scalia."