An effort by Pennsylvania Republican insiders to derail State Sen. Doug Mastriano’s march to the gubernatorial nomination made little headway Wednesday, as his top rivals vowed to stay in the race and showed no sign of coalescing behind a single alternative.

“No white smoke,” said a person familiar with the eleventh-hour plan, jokingly referring to how the election of a new pope is announced.

But some Republicans were still holding out hope for a Hail Mary, fearing Mastriano would lose badly in a general election — despite a national political environment that’s widely seen as favorable to the GOP. Former U.S. Rep. Lou Barletta’s campaign said late Wednesday afternoon he would be joined Thursday morning in Harrisburg by rival Jake Corman, the state Senate leader, for a “major campaign announcement.”

Corman is expected to endorse Barletta in the May 17 primary election — and GOP insiders were hoping to recruit other candidates to join him, people familiar with the matter said. Former U.S. Rep. Melissa Hart was among those said to be considering joining.

But Corman and Hart have been polling in the low single-digits, and there was no sign that the two remaining top contenders in the race — former Delaware County Councilman David White and former U.S. Attorney Bill McSwain — were ready to back Barletta.

“It’s all up for grabs,” McSwain said in a radio interview Wednesday with the Rich Zeoli Show, adding that he believes he’s best situated to defeat state Attorney General Josh Shapiro, the presumptive Democratic nominee. “If there’s any sort of backroom dealing like you’re referring to, people should coalesce behind my campaign.”

He noted that most polls show a substantial share of voters remain undecided.

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For his part, Mastriano posted on Facebook an image of an Inquirer article detailing the last-ditch effort. “It’s the Establishment vs. The People. And come May 17, The People are going to win!” Mastriano wrote.

Some Republican leaders, citing internal polls, believe Mastriano would not only lose in November, but also potentially jeopardize Republicans in other races.

And on Tuesday, National Journal reported that the Republican Governors Association was unlikely to spend money in the Pennsylvania election if Mastriano wins the nomination. The RGA, which started reserving airtime for TV commercials in other battleground states in March, has not booked airtime in Pennsylvania — despite the fact that Shapiro has been the de facto Democratic nominee for months.

Mastriano drew national attention for his efforts to overturn the results of the 2020 presidential election and his presence at the Jan. 6, 2021, rally that led to the Capitol attack. The congressional committee investigating the attack has subpoenaed Mastriano for documents and testimony. During a debate last month, Mastriano said he would not face legal trouble over the matter.

Asked during an interview with the conservative news outlet Delaware Valley Journal about Jan. 6 and his attendance at a conference last month that featured a video promoting QAnon and conspiracy theories about the Sept. 11 terrorist attacks, Mastriano lashed out before abruptly hanging up the phone. “You’re talking like an East German there,” he told the host.

Mastriano has been at or near the top of polling in the race for months, but his status as the undisputed front-runner wasn’t entirely clear until recent weeks. Some party insiders held out hope that former President Donald Trump would help clear the field by endorsing one of Mastriano’s rivals.

But Trump made no such announcement during his rally last Friday in Western Pennsylvania. That — combined with Shapiro’s airing of TV ads aimed at boosting Mastriano in the primary — sent some establishment Republicans into panic mode.

“Everyone is kind of losing their minds,” said a GOP operative familiar with the developments.

Some of those establishment figures commissioned a poll with the hope that the survey — independent from the campaigns — would show which candidate had the best chance to beat Mastriano. The poll, these insiders hoped, would help broker a deal to endorse one candidate.

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Over the weekend, state party caucus chairs from regions across the state held a strategy call with Andy Reilly, the state’s Republican national committeeman, according to multiple sources briefed on the matter. State party chairman Lawrence Tabas joined in a subsequent call, the sources said, and reiterated his position that the party should not intervene — consistent with a vote by state committee members in February not to endorse in the race.

Some in the party say Tabas should have done more to weed out lower-tier candidates months ago. The state party didn’t immediately return a message seeking comment.

In an email to GOP insiders Monday, Tabas said: “With more on the line than any time I can remember, I urge you to remember that Democrat leaders’ strategy is to turn us on ourselves.”

“There is nothing more true and sincere that I can convey to you than this: Democrats know they can beat us if we are divided,” Tabas said in the email, which was obtained by The Inquirer. “The[y] know they have no shot if we are united. I urge you to vote on May 17 for the candidate you believe will best unite us and push us to victory in November.”