The Senate’s top Democrat accused Republicans Monday of trying to delegitimize Barack Obama’s presidency by preventing him from filling the Supreme Court vacancy as a divided Senate convened for the first time since Antonin Scalia’s death and immediately dove into election-year combat over the opening.

Firing back, Republicans highlighted June 1992 remarks by Vice President Joe Biden, who chaired the Senate Judiciary Committee at the time. Biden argued then that should a Supreme Court seat become vacant — there was no opening at the time — then-President George H.W. Bush should not nominate a replacement until after that fall’s presidential election.

The back-and forth underscored the high-stakes political showdown that Scalia’s death has sparked, a clash that each party thinks will motivate its voters to stream to the polls in November. The Supreme Court now faces a precarious 4-4 ideological balance between right- and left-leaning justices as they consider cases on abortion, voting rights, Obama’s health care law and other polarizing issues, and in

Senate Minority Leader Harry Reid, D-Nev., said Republicans were making “an unprecedented attempt to hold hostage an entire branch of government.”

In sharp tones that typified both sides’ comments since the 79-year-old jurist’s Feb. 13 passing, Reid added that Republicans are pressing “a full-blown effort to delegitimize President Barack Obama, the presidency, and undermine our basic system of checks and balances.”

While Senate Majority Leader Mitch McConnell, R-Ky., began Monday’s Senate’s session by praising Scalia, his own press office and the GOP chairman of the House Judiciary Committee fired back by citing the 1992 Biden remarks.

“Once the political season is underway and it is, action on a Supreme Court nomination must be put off until after the election campaign is over,” Biden said at the time on the Senate floor, according to a C-SPAN recording of his remarks.

Sen. Charles Grassley, R-Iowa, who heads the judiciary panel, called the remarks “The Biden Rules” and said the vice president “knows what the Senate should do.”

The White House had no immediate response to the video. Both sides have spent days unearthing comments members of the other party made about court nominations years ago under presidents of different parties.

McConnell has said the president elected this November should nominate the replacement. That assertion that has drawn support from nearly all Republicans and irate, solid opposition from Democrats.

As the two parties girded for what promises to be a months-long battle, Sen. Mark Kirk, R-Ill. — who faces a difficult re-election race this year in a Democratic-leaning state — distributed an opinion column he’d written for the Chicago Sun-Times saying he looks forward to Obama selecting a nominee.

“I also recognize my duty as a senator to either vote in support or opposition to that nominee following a fair and thorough hearing along with a complete and transparent release of all requested information,” Kirk wrote. “The Senate’s role in providing advice and consent is as important and significant as the president’s role in proposing a nominee.”

Obama is expected to announce his nomination in coming weeks. While McConnell has said he favors “deferring action in the Senate” until the voters have selected a new president, GOP senators will gather on Tuesday for the first time since Scalia’s death to discuss their path forward.

Unanswered questions were making it tough for Republicans to fine-tune their approach just yet, including who Obama will name and who the GOP presidential nominee will be. Another challenge was how GOP senators facing re-election in closely divided states would strike a balance between retaining conservatives’ support and avoiding accusations from independent voters of being too partisan.

One of those senators, Kelly Ayotte, a New Hampshire Republican, displayed no such concerns Friday. She tweeted, “W/ so much on the line, Senate should not proceed w confirmation process until American ppl have spoken by electing a new president in Nov.”

Outnumbered Democrats were solidly behind Obama but seemed to face an uphill climb. They were strategizing over how to maximize pressure on Republican senators, including Ayotte, Kirk and three others seeking re-election in states Obama won in both 2008 and 2012: Ohio, Wisconsin and Pennsylvania.

Recent decades have seen other pitched battles over Supreme Court selections, including Robert Bork’s 1987 rejection and Samuel Alito’s confirmation in 2006. Yet it’s unusual for the Senate to wage titanic struggles over the selections, or take no action at all.

Since 1789, presidents have sent 160 Supreme Court nominations to the Senate, according to the nonpartisan Congressional Research Service. Of those, 124 were confirmed.

Only 12 nominations have not reached the Senate floor, including just five instances in the 20th and 21st centuries.

(AP)