The late Supreme Court justice Antonin Scalia (left) and PA Sen. Pat Toomey, up for re-election in November.

Updated 4:15 p.m. Monday

Get used to hearing Republican Senator Pat Toomey’s name.

The unexpected death of Supreme Court Justice Antonin Scalia on Saturday sent Washington and the battle for the White House into a frenzy over the politics of deciding his replacement, and soon enough the political battle over his seat could lead to a deluge of political ad spending in the Keystone State.

Any presidential nominee to the court — for President Obama, likely a left-leaning candidate — would have to be confirmed by the Senate, where Republicans currently hold a 54-46 majority. Within a few hours of Scalia’s death, GOP majority leader Mitch McConnell, of Kentucky, vowed that the next president should nominate the conservative justice’s successor. Further, Republican senators could block any movement toward a vote on a new justice.

That’s why Toomey, up for re-election in November and considered one of the most vulnerable senators in 2016, could play a key role in the future of not only the senate, but of the Supreme Court and the cases it could decide in the coming years: Everything from abortion rights to campaign finance reform to ending the death penalty.

In a statement released Monday afternoon, Toomey said the next president should decide Scalia’s replacement, effectively saying the GOP should block an attempt by the Obama White House to name a liberal successor (thus tipping the scales of the court in the favor of Democrats for the first time in decades).

As Daily News columnist Will Bunch pointed out, senators facing tough re-elections this year, including Toomey, will face attacks lobbed at them by Democrats if they block a vote. They’ll be told they’re contributing to congressional dysfunction and are the ones most likely to buck Republican leadership and approve an Obama nominee.

But beyond that, if many pundits are right and the GOP is successful in blocking an attempt by Obama to name a new justice to the court, the November elections in states where Republican senators could lose their seats will become critical. If the GOP loses its majority in the Senate, everything changes. Pat Toomey’s seat in Pennsylvania is crucial to that.

Here’s why, and how Philadelphia in particular comes into play:

The Senate make-up and its court impact

Without Scalia, a staunch conservative, the Supreme Court is expected to fall to 4-4 ties on a number of issues as four liberals and four conservatives remain.

His death set off politicization shortly after news broke, largely because it’s the first time in Obama’s presidency that he has the opportunity to switch the party leaning of a conservative seat on the bench. His two previous nominees were approved by the Senate but weren’t as contentious, largely because they were both replacing liberal justices. The GOP’s majority on the court was still protected.

But it’s now an election year. Sen. Ted Cruz, R-Texas, a presidential candidate who clerked for the Supreme Court and sits on the Senate Judiciary Committee, has said he’ll filibuster any Obama nominee to the court and says it should be up to the next president to decide the fate of Scalia’s seat.

That’ll work out well for Republicans if they win the presidency and retain control of the Senate. Even if they lose the White House, GOP control of the Senate could force a Democratic president to nominate a moderate to the court so the nominee is actually confirmed by the Senate.

But everything changes if Democrats gain control of the chamber after the November election.

If Democrats were to win control of the Senate and the presidency, the court tilts further left, according to conventional thinking. And it could just be the start. Both Ruth Bader Ginsburg, 82, and Justice Stephen Breyer, 77, are reaching retirement age and could step down to allow a Democratic president to choose younger successors.

Justice Anthony Kennedy will be 80 in 2017 and though he’s a conservative, he could also be retiring within the time period of the next president. If either Hillary Clinton or Bernie Sanders has the ability to nominate four justices in total to the Supreme Court, he or she — with the help of a Democratic Senate to confirm — could be effectively deciding the liberal majority of the Supreme Court for two decades.

Why Pennsylvania matters

Because one third of the senate is up for re-election every two years, there are 34 seats facing re-election in 2016 and of those, Democrats hold 10. In order to regain control of the Senate, Democrats would have to gain five seats (or four if a Democrat wins the presidency because ties in the Senate are broken by the VP.)

National Democrats are focusing their efforts by working to defeat Republican senators in five states that can be considered blue because Obama carried them twice in presidential elections: Those states are Ohio, New Hampshire, Wisconsin, Illinois and, of course, Pennsylvania.

For the last year, Toomey has shown up on multiple lists as one of the senators most in danger of losing his seat to a Democrat. He’s also been accused of slow-walking judicial nominations for appointments to lower courts and blocking his own appointments.

Toomey isn’t facing a primary challenge, but three Democrats are vying in the primary for a chance to challenge him. Among them is former Congressman Joe Sestak, who ran against Toomey in 2010 and lost after garnering 49 percent of the vote. He’s facing Gov. Tom Wolf’s former Chief of Staff, Katie McGinty, who’s so far drawn the most flak from the state GOP, and small-town, western PA Mayor John Fetterman, a charismatic dark horse pick who’s drawn some national headlines.

The Democrats’ donor base in Pennsylvania is largely fractured between the three, and recent polls don’t show one candidate largely defeating another in the primary as a high number of PA Democrats remain undecided. Meanwhile, cash has poured in for Toomey, and with the Supreme Court on the line, that’ll only increase as the general election draws near.

The incumbent senator had a hefty war chest going into 2015 and by the end of the year, he had $9.6 million in his campaign coffers. Compare that to Sestak, who had $2.4 million in the bank last fall, and McGinty, who raised nearly $2 million between August and December of last year. Toomey will also spend wayyyy less cash this spring than Sestak, McGinty and Fetterman who are all dealing with the primary.

Of course, it’s the general election in November that matters here and a strong Democratic turnout, especially in a presidential election year, could greatly influence Toomey’s fate. That’s where Philadelphia comes in.

Philly’s role in the general election

There are about a million more registered Democrats in Pennsylvania than there are Republicans. Literally one million. That’s why Pennsylvania has gone blue in presidential election years since 1988 and why Toomey’s especially vulnerable this time around — last time he was up for election, it didn’t fall in a presidential election year and voter turnout wasn’t as strong.

In 2010, Toomey beat Sestak statewide by just 80,000 votes. In Philadelphia where registered Democrats greatly outnumber registered Republicans, Sestak garnered nearly 300,000 more votes than Toomey did and about 423,000 Philadelphians showed up to the polls that year.

The election in 2016 will be different because voter turnout is historically higher in presidential election years. In 2008 when Barack Obama faced John McCain for the presidency, more than 715,000 people came to the polls to cast a ballot — about 600,000 of them were for Obama.

That’s a turnout difference of nearly 300,000 people in Philadelphia alone. If those voters showed up in 2010, it could have tipped the scales in Sestak’s favor because of Philadelphia’s heavy Democratic registration.

But they didn’t. With 2016 being a presidential election year, maybe this time around, they will. Whoever the Democratic nominee is against Toomey could greatly benefit from a high voter turnout in Philly, and thus, so could the Democratic party as it tries this fall to grab the White House, the Senate and, from there, the Supreme Court.

That of course assumes the Senate race will be as close as it was in 2010, and early indications show it might not be. The Democratic primary in Pennsylvania of course hasn’t played out yet. And for all we know, maybe the Senate GOP won’t block a moderate Supreme Court nomination by President Obama and the leaning of the court won’t be dependent upon how America — and Pennsylvania — votes in November.

Or maybe the future of the country could be decided based on which party controls the Senate, which could come down to the GOP holding tightly onto just four seats, Toomey’s being one of the most important.

That means voter turnout in Pennsylvania and, by extension Philadelphia, could ultimately play a role in changing the high court and ushering in a more liberal America.

Anna Orso was a reporter/curator at Billy Penn from 2014 to 2017.