SCOTUS rejects GOP challenge to new Pennsylvania House map in boost to Democrats It is the second time on Monday Republicans received a judicial blow.

The U.S. Supreme Court has denied a GOP-led request to hold off using a new House map for the state of Pennsylvania, meaning candidates — including Republican Rick Saccone and Democrat Conor Lamb - lawmakers who recently faced off in a tough battle in the state — will run in new districts this November.

The move is a blow to Republican hopes and a boost to Democratic chances of retaking control of the House of Representatives.

It was the second time Monday that Republicans lost in the courts. Earlier, a three-judge panel in Pennsylvania upheld the state’s new congressional map.

The Supreme Court announced, "the application for stay presented to Justice Alito and by him referred to the Court is denied." It's of note that Justice Samuel Alito referred the request to the full court. In February, Alito denied a request by Republicans for a stay of the new map and was criticized for not consulting the rest of the court, which he was not legally required to do.

With few, if any, legal options left — and the filing deadline for House candidates on Tuesday — Republicans conceded the battle Monday evening.

State House Speaker Mike Turzai said in a statement: "We respect the decision of the U.S. Supreme Court and are prepared to move on to other issues of importance to the people of Pennsylvania.”

Republicans in the state had filed for a stay against the new map, which was drawn by the state Supreme Court after the Democratic governor and GOP-controlled state legislature could not come to terms on a new one.

The GOP took two legal routes — one before the U.S. Supreme Court and the other before the federal panel.

They lost on both.

Democrats are expected to pick up three to five House seats under the new map, according to estimates by election experts, which would help them on their way to the 24 seats they need to retake control of the lower chamber of Congress.

"It provides a truly level playing field" for congressional districts in the state, Democratic state Party Chairman Jack Hanna told ABC News of the Supreme Court decision.

He noted the party is hopeful it will pick up "maybe three seats."

Earlier Monday, a three-judge panel ruled that state Republicans had no standing to make their argument when requesting their stay for the map. The court also noted that “because fundamental principles of Constitutional standing and judicial restraint prohibit us from exercising jurisdiction, we have no authority to take any action other than to dismiss” the request.

In January, the Pennsylvania Supreme Court ordered a new House map drawn, citing gerrymandered districts that favored Republicans. The GOP has been fighting the court order ever since and the U.S. Supreme Court denied an early request to put a stay on the map.

Republicans currently hold 12 of the state's 18 congressional districts, while Democrats control just five. The special election last week for Pennsylvania’s 18th Congressional District was held under the old map.

Lamb and Saccone — the two candidates who gained national attention in their contest — will seek reelection different districts.

Lamb will run in state's new 17th Congressional District this fall, setting up a likely match with GOP Rep. Keith Rothfus.

And Saccone is gathering petitions to run in the new 14th Congressional District in November.

If they win their respective races, Saccone and Lamb, the former rivals, could serve together representing Pennsylvania in Congress next year.

Several GOP lawmakers found their House districts dramatically affected by the new map, including Rep. Ryan Costello, who is considering retirement, several state and national officials in GOP politics told ABC News.

His 6th Congressional District was transformed from one that Hillary Clinton won by one point in 2016 to one she would have won by nine points.

Costello has not said he is retiring and his office and campaign did not respond to ABC News' multiple requests for comment.

If he files his balloting petitions on Tuesday and later decides to retire, there is a procedure for the state party to replace him as a candidate on the ballot.

Pennsylvania’s House delegation took a big hit in losing Republican members this year.

GOP Rep. Tim Murphy resigned after a scandal. Rep. Lou Barletta is running for Senate. And Reps. Bill Shuster, Charlie Dent and Patrick Meehan are retiring.