The Commonwealth Partners Chamber of Entrepreneurs, a major conservative group, has switched its endorsement in the Pennsylvania Republican gubernatorial primary to former Rep. Lou Barletta (R-PA) and is calling on his fellow GOP candidates to drop out and do the same.

In a statement on Sunday evening, Commonwealth Partners President and CEO Matt Brouillette announced that the group was switching to Barletta after having backed former United States Attorney Bill McSwain in the primary.

The goal, Brouilette said, should be coalescing voters around defeating Democrat gubernatorial candidate Josh Shapiro. State Sen. Doug Mastriano (R), Brouilette said, would not be able to pull swing voters into that coalition in a general election.

“It’s become abundantly clear in recent days that nominating Lou Barletta for governor is Republicans’ best chance to defeat Josh Shapiro in November,” Brouillette said.

He explained:

Months ago, Commonwealth Partners began cautioning of the dangers of nominating Doug Mastriano, as he would not be able to win the swing voters necessary to win in November. No other organization has come close to spending the millions our connected political action committee has spent to educate voters about the dangers of a Mastriano nomination. [Emphasis added]

Unfortunately, although Mastriano is garnering support from less than 30 percent of likely primary voters, given the large field of candidates, this could be enough to secure him the nomination. [Emphasis added]

At the end of the day, Commonwealth Partners is about a cause, not about a particular candidate. That’s why today, we are endorsing Lou Barletta for governor, and it’s why we will continue our call for Bill McSwain and Dave White to withdraw from the race and do the same for the good of our commonwealth and our country. [Emphasis added]

In an exclusive interview on Sunday, Barletta also called on McSwain and former Pennsylvania GOP official Dave White to drop out of the race and endorse his candidacy.

“I really hope that Dave White and Bill McSwain would see that as well — that I’m the one person, I’ve been at the top of every poll with Doug Mastriano since the day I announced,” Barletta said. “And they have spent over $20-something million on their campaigns and haven’t gotten above me once.”

Former President Trump has endorsed Mastriano in the race, sending shockwaves through Republican officials in Pennsylvania who fear the state senator will fail at winning a general election.

An Osage Research poll of 600 swing voters in Pennsylvania shows Mastriano is losing in a head-to-head matchup with Shapiro.

While swing voters, by a three percent margin, say they prefer a Republican to a Democrat for governor, 49 percent said they would vote for Shapiro if Mastriano is the GOP nominee. Mastriano trails in the matchup, with just 41 percent.

The Pennsylvania GOP gubernatorial primary election is on May 17.

John Binder is a reporter for Breitbart News. Email him at jbinder@breitbart.com. Follow him on Twitter here.