MECHANICSBURG, PENNSYLVANIA — In picking a sure thing by endorsing state Sen. Doug Mastriano for governor in Pennsylvania, former President Donald Trump has set off a chain of events that could cost Republicans the governor's office and ensure him a tough race in Pennsylvania if he chooses to run for president in 2024.

Allegheny County Republican Party Chairman Sam DeMarco was stunned when the news hit social media: “I am very disappointed with the president's decision in picking Mastriano. It's not exactly going out on a limb supporting someone in the lead three days before the election; it does guarantee him one win in this state on Tuesday,” said DeMarco in an interview with the Washington Examiner.

Jackie Kulback, the head of the Cambria County Republican Party, a grassroots powerhouse who just recently took this post-industrial county from a Democratic-majority county to a Republican one, was furious at Trump’s decision to back Mastriano.

Kulback, who has an army of volunteers set to work on Tuesday to get voters out, told the Washington Examiner: "Trump’s interference in Pennsylvania is going to cost us the governor's office in the fall, which, by the way, is very important to hold when you are running for president in 2024, but there is a chance it could also cost us the Senate seat."

The Cambria County Republican Party suggested either Dave White or Lou Barletta for the party’s nominee for governor.

One prominent county chairman, who asked to remain anonymous but has hosted Trump in his county several times and voted for him twice, said, “Maybe Joe Biden’s not the only septuagenarian who should take a competency test?”

The county leaders were all concerned that this endorsement might lift up Kathy Barnette over the finish line in the Senate race, guaranteeing that seat would also be lost in the fall. But they also agreed Barnette had recently faded under scrutiny and might not win.

Washington County Republican Chairman Dave Ball, who helped turn a majority-registered Democratic county into a majority-registered Republican one, failed to understand the whys of Trump’s decision, “other than, of course, he gets to claim a win, which is something he likes to brag about.”

Ball, who famously said, “What the hell was he thinking?”, after Trump announced his support for Dr. Mehmet Oz in the Senate race over David McCormick, had stronger words about Trump’s decision to back Mastriano, but he decided to leave those up to the imagination of the reader.

“The president's endorsement of Mehmet Oz was very hard to understand to begin with; now we have a three-way, a very tight three-way race for the critical Pennsylvania Senate seat, and to most of us, it appears that Oz is beginning to fade. So, what does the president do? He's going to shore that up somehow and endorse a sure thing — it is very disappointing,” said Ball.

A central county chairman, who asked that his name not be used, said he deeply resents Trump being involved in Pennsylvania: “This marks the beginning of the end of the Trump era — he endorses a front-runner, and he will claim responsibility for the victory,” he said of the endorsement.

“Whether you like Mastriano or not, I don’t, he has however understood what really upset a certain portion of the voters, and he addresses them. When he wins, Mastriano is responsible for his pending victory, but Trump will not have anything to do with it,” he said.

Ball said many supporters of Trump justify their support for Mastriano because they think he will win in November like Trump did in 2016. “Well, Mastriano is no Trump. Trump, at the time, at least understood you need to build a coalition,” he said.

DeMarco said Trump may as well have announced he was not going to run in 2024 because Democrat Josh Shapiro would easily beat Mastriano in 2022 and make it hard for Trump to win the state in 2024.

Kulback said Trump’s interference in Pennsylvania would be costly: “It will cost a very winnable governor's seat. Dave White or Lou Barletta could have easily beat Shapiro in the fall in a very good year for Republicans.”

She also worries that Mastriano will take Barnette (who has been campaigning with him for months) over the finish line, “although it appears as more people know about her, she has peaked.”

Several other county leaders echoed the same sentiments — almost all believe this move will cost Trump support in Pennsylvania if he runs again in 2024.