WASHINGTON — As Steve Bannon opens up his war on the Republican establishment, an unlikely Pennsylvanian appears ready to enlist.

Jeff Bartos, a Montgomery County businessman running an uphill Senate campaign, staked a claim to the antiestablishment mantle last week by writing that he "will not pledge" to support the GOP's Senate leader, Mitch McConnell, a figure of growing antipathy among Republican voters and particularly Trump supporters.

He posted the declaration on Breitbart, the right-wing news site where Bannon is executive chairman. Bartos had previously met twice with Bannon, the former chief strategist to President Trump, to discuss his campaign to win the GOP nomination to take on Democratic Sen. Bob Casey next year.

Bartos' move was surprising on several levels — not least because he donated $1,000 to McConnell's 2014 reelection campaign and because he has had close ties to the GOP elite. Bartos previously served on the board of a political committee run by Bob Asher, a prototypical Republican insider and fund-raiser who serves as Pennsylvania's national GOP committeeman, and has donated to many traditional Republicans, including Pennsylvania Sen. Pat Toomey.

But with much of Pennsylvania's GOP establishment expected to line up behind U.S. Rep. Lou Barletta in the Senate primary next year, Bartos seems to be taking a page from Alabama's Roy Moore.

Moore upset party insiders and won a Republican primary last month in large part by casting McConnell as a villain who hasn't effectively helped the president. His campaign captured the fervor of Trump supporters — even though Trump supported his opponent — and drew backing from Bannon, who has declared war on McConnell and GOP incumbents in an escalating battle for the direction of the Republican Party.

"Obviously I would want Steve's support, but I want the support of a lot more people as well," Bartos said in an interview, confirming his meetings with Bannon, including one over the summer.

He described himself as "a political outsider running as a first-time candidate" and said, "I want support from anyone in the commonwealth of Pennsylvania and I want support nationally from anyone who elects outsiders."

Bartos, of Lower Merion, personally knows at least one close Bannon adviser: Alexandra Preate, a Pennsylvania native who works as a Bannon public relations strategist. Her twin sister, Elizabeth Preate Havey, is the Republican chairwoman in Bartos' hometown. (Their father is former Pennsylvania Attorney General Ernie Preate.)

"Jeff is still gambling that he can get the rank and file to oppose" Barletta, said one Republican who is familiar with the political jockeying but who requested anonymity to describe the maneuvering. "He is playing up to Bannon and the Bannon people."

Barletta, however, has been one of Trump's most vocal allies. The president singled out Barletta and his Senate campaign at a rally this month near Harrisburg. It's unclear if Bannon has any interest in backing Bartos. A spokeswoman did not respond to a request for comment.

And Bartos' opposition to McConnell wasn't exactly ironclad.

"Until the dysfunctional Senate leadership shows that they can deliver for the people who support the president's agenda, I will not pledge to vote for Mitch McConnell for Republican Leader," he wrote on Breitbart.

He did not, however, promise to vote against McConnell (despite a Breitbart headline suggesting otherwise), and his wording left room to eventually back the Senate leader.

Bartos said he might support McConnell if Congress advanced "meaningful" health-care reform, a tax overhaul, and a rules change that would help confirm Trump nominees by eliminating "blue slips" that effectively give home-state senators veto power over a president's choices.

But he said he has heard widespread disappointment with the Senate leader as he has traveled Pennsylvania.

"People were really excited about the president's reform agenda," Bartos said. "They're frustrated it's not being implemented quickly enough."

He disputed the idea that his links to the party's elite dent his outsider claims, noting that he is a businessman in his first-ever run for public office — a contrast he has used to attack both Casey and Barletta, who is now in his fourth term in Congress after serving as mayor of Hazleton.

"People genuinely gravitate to a candidate who's signed the front of a paycheck," Bartos said.

He wouldn't rule out one rumor that has gained steam in Republican circles: that he might shift races and run for lieutenant governor instead.

"I'm running hard for the United States Senate," Bartos said, but when pressed added, "You never rule out anything."

Even if he did change races, Bartos' stand against McConnell could ingratiate him with the Trump base, said Josh Novotney, a Republican consultant based in Philadelphia.

"If you don't have a voting record, you can define who you are pretty easily," he said.

Barletta's campaign did not respond to a request for comment on Bartos, or on whether he would support McConnell, whose approval rating has plunged, even among Republicans.

Normally, it would be political suicide to attack one of your own party's top officials. But these days, even insiders want outsider cred.