Pennsylvania state Sen. Doug Mastriano (R) announced Thursday night he will not run for the U.S. Senate in Pennsylvania, allowing Republicans to breathe easy and opening a clear path for David McCormick to take on Sen. Bob Casey (D-Pa.) next year.

Mastriano made the news official during a Facebook Live event mere months after he lost the state’s gubernatorial contest to Gov. Josh Shapiro (D) by nearly 15 points.

“At this time, we have decided not to run for the U.S. Senate, but to continue to serve in Harrisburg,” Mastriano said. “I know for some that will be disappointing. For others, it won’t be disappointing because you’re like, ‘Who’s going to fill his seat? Who’s going to be our voice in Harrisburg?'” 

“We need to beat [Casey]. While I have decided not to run, someone else will decide to run, and someone else will win the primary next year and be the nominee. Whoever is that nominee, I will support them,” he continued. “We hope you will too because I don’t want any other Republican candidate to go through what we went through last year when our own party betrayed us.”

A bid by Mastriano, a hard-line conservative who won former President Trump’s endorsement in 2022, would not have been greeted kindly by many top Republicans, who believe that in losing the governor’s mansion, he hurt the party in congressional contests and in state legislature races, including the GOP’s loss of the state House. 

Mastriano’s decision means the road is wide open for McCormick, who narrowly lost the state’s GOP Senate primary last year to Mehmet Oz, to nab the party’s nomination to take on Casey. 

McCormick has yet to decide on whether to launch a second straight Senate bid, but he is expected to do so later this summer or in the fall as establishment GOP forces line up behind him.

“I thank Doug for his years of military and public service and his dedication to Pennsylvania,” McCormick said in a statement. “I am seriously considering a run for the U.S. Senate because Bob Casey has consistently made life worse for Pennsylvania families over the past 18 years, and our state deserves better.”

“We need a Republican nominee who can build a broad coalition of Pennsylvanians to defeat Bob Casey and improve the lives of Pennsylvania families,” he added.

The potential candidate-in-waiting has remained in the news throughout the year with the rollout of a book and an ongoing book tour. He has also kept up meetings across the state with party leaders, including at the county level. 

Among those pushing for him to run is Sen. Steve Daines (R-Mont.), the chairman of the National Republican Senatorial Committee, who has made clear he believes McCormick is the type of candidate who can win a primary and a general election matchup against the three-term Senate Democrat with a legendary name in Pennsylvania politics. 

“[McCormick] would be a candidate that I think unites Republicans in Pennsylvania and he’d be a very strong candidate in the primary and the general,” Daines said in March.

In addition, the Senate Leadership Fund, which is run by allies of Senate Minority Leader Mitch McConnell (R-Ky.), has also signaled its backing of the former Bridgewater Associates CEO. 

The Pennsylvania Senate contest is widely expected to be one of the most expensive on the 2024 map, with sources telling The Hill the nominee is expected to need at least $100 million for the potential brawl. McCormick could dip into his own bank account to help fund his efforts, though he is not expected to do so after he dropped $14 million into last year’s primary contest in only five months.

Casey won his seat in 2006 by defeating then-Sen. Rick Santorum (R-Pa.). He has also handily won reelection twice, having most recently defeated then-Rep. Lou Barletta (R-Pa.) by a 13-point margin. 

Democrats had been salivating at the possibility of Mastriano entering the race. Shapiro’s team last year spent $3 million to boost Mastriano in a seven-candidate field and ensure he would be their general election opponent. 

“Tonight Mastriano threatened that he and his supporters will continue looming over Republicans in Pennsylvania, which will make their Senate Primary dynamics in even messier — and guarantee whichever candidate emerges will be badly damaged and out of step with the voters who will decide the general election,” the Democratic Senatorial Campaign Committee said in a statement.

Mastriano’s performance last year also seemed to turn off former President Trump, who reportedly was opposed to him entering the race and did not plan to endorse him in a potential Senate bid. 

Trump, of course, spoke harshly of McCormick during his Senate bid last year, likening him to former Sen. Pat Toomey (R-Pa.), who voted to convict the president in his second impeachment trial over his role in the Jan. 6 attack on the Capitol, and called him a “liberal Wall Street Republican.”