WASHINGTON -- Supreme Court Justice Antonin Scalia's death has raised the stakes for Pennsylvania's U.S. Senate race and given Democrats a new pressure point they hope to wield against the incumbent Republican, Pat Toomey.

One of Toomey's prime re-election arguments has been that the GOP-led Senate has been far more productive and open than it was in Democratic hands. And he has often boasted about his cooperation with Sen. Bob Casey (D., Pa.) in vetting and approving federal judges in Pennsylvania.

But as battle lines emerged over whether the GOP will allow a Senate vote on any nomination President Obama puts forward to replace Scalia, Toomey on Monday joined fellow Republicans in arguing that the next president should pick Scalia's replacement. He said any Obama nominee will be rejected, and that no pick is likely to meet the added scrutiny deserved less than a year before voters give the nod to a new chief executive.

"Given that we are already well into the presidential election process and that the Supreme Court appointment is for a lifetime, it makes sense to give the American people a more direct say in this critical decision," Toomey said in a news release. He added, "There has already been too much politicking around the issue of (Scalia's) replacement. This decision should not be rushed, and it should not be made amid the clamoring of a presidential election season."

Toomey's statement came as Democrats warned that he and other swing-state Republican could pay a political price if they refuse to allow a fair hearing.

"The next President doesn't take office for another 340 days. During that time the Senate has an obligation to the American people to do its job," wrote Casey spokesman John Rizzo.

The Democrats running to challenge Toomey this fall seized the issue Monday morning.

"For Senate Republicans to put politics ahead of their Constitutional duty would be an insult to (Scalia's) legacy," said Katie McGinty, one of three Democratic Senate candidates.

Another, Braddock Mayor John Fetterman, issued a release asking Toomey: "Who do you work for: the citizens of Pennsylvania or Ted Cruz and other extreme GOP obstructionists?"

McGinty, Gov. Wolf's former chief of staff, Fetterman and Joe Sestak, a former congressman and admiral, are running to challenge Toomey in what was already expected to be a hotly-contested race that could swing control of the Senate.

Sestak wrote on Twitter that Toomey should fulfill his duty and "stand with PA, not partisan obstructionism."

Toomey's campaign fired back that he "has demonstrated a clear record of bipartisanship when it comes to approving judges – Joe Sestak and Katie McGinty have never demonstrated any interest in working across the aisle about anything."

The Pennsylvania race was already expected to be one of the toughest in the country, with the potential to swing control of the Senate. Now the balance of the high court has also been thrust into the battle.

Obama hopes to replace Scalia, a conservative giant, with one of his own picks. If he fails, and either party captures both the White House and Senate this fall, it would have much more power to push for a sharply conservative or liberal nominee.

Every other senator from the Philadelphia area (all of them Democrats), has said the Senate should vote.

Democrats argued that vows to block Obama -- before his nominee has even been named -- will backfire in the moderate states such as Pennsylvania, where Republicans are defending several key seats.

"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," Sen. Patrick Leahy (D., Vt.), the top Democrat on the judiciary committee, told CNN's "State of the Union" Sunday.

Republicans, however, have said a president in his final year in office should not make a lifetime appointment that could change the shape of the court, and the nation's laws, for decades to come. Hours after Scalia's death, Senate Majority Leader Mitch McConnell said there would be no vote on anyone Obama nominates.

"The American people‎ should have a voice in the selection of their next Supreme Court Justice," McConnell, of Kentucky, said in a statement. "Therefore, this vacancy should not be filled until we have a new president."

Key GOP senators joined his call, and Cruz, a top Republican contender in the presidential race, vowed to use the filibuster to block any possible vote on an Obama nominee.

Fights over judges have animated the Republican base as conservatives have chafed at recent decisions on issues such as the Affordable Care Act and same-sex marriage.

And, some argue, Republicans could point to the fate of the court as another reason to leave the Senate in GOP hands, to serve as a check on any push to install a liberal justice who might shift the balance of the closely-divided court.

"If anyone thinks the center of the electorate is clamoring for Obama to name another left-wing jurist they're nuts," Josh Holmes, McConnell's former chief of staff, told the New York Times.

At least three other Republican senators facing difficult re-elections in blue-leaning states have supported the idea that the Senate should wait for the next president to take office: New Hampshire's Kelly Ayotte, and Wisconsin's Ron Johnson. Ohio's Rob Portman later joined them as well.

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