The Republican establishment that Steve Bannon is agitating to overthrow is welcoming the nationalist firebrand through the front door to pitch his rebellion to the party faithful.

The California Republican Party's fall convention this past Friday; Washington's conservative Hudson Institute think tank on Monday; and a scheduled Macomb County, Mich., GOP "unity" dinner on Nov. 8.

Bannon is leveraging his connection with President Trump in these settings to urge grassroots conservatives and Republican insiders to oust party leaders in Congress and discard decades of traditional policy.

"It's a forum to continue his war to destroy the GOP from the inside," said a Republican strategist, who requested anonymity in order to speak candidly.

Bannon, at the helm of Breitbart News, was the CEO of Trump's presidential campaign and then served as his chief strategist in the White House before exiting in August.

That relationship, combined with Republican voters' rising frustration with the GOP-controlled House and Senate, has earned Bannon and his 2018 insurgency strategy a modicum of credibility with Republican donors and activists that don't typically consort with anti-establishment instigators.

Bannon is raising resources and recruiting challengers to run against Republican incumbents in Senate primaries, even those loyal to Trump, in a bid to depose Senate Majority Mitch McConnell, R-Ky. Bannon is similarly hostile to House Speaker Paul Ryan, R-Wis., though he hasn't made a concerted move to toss him.

It's nothing new for Bannon, who led Breitbart before joining the Trump campaign and used the outlet as a platform to undermine the Republican establishment from the outside. Now, he is using his prominence to weaken it from the inside. Republican voters are granting him an audience.

"Ticket sales are great. People want to hear the guy," a Republican insider in Michigan said Monday, regarding the Macomb County GOP's "Lincoln/Reagan Unity Dinner."

The Macomb County GOP could not be reached for comment on its decision to tap Bannon as a headliner for what is essentially dinner to raise money despite his threats on against party leaders and questioning of some closely held party policy on domestic and foreign policy issues.

In part, the decision is financial. Creating excitement around local party events can be a challenge.

Bannon might not sell everywhere. But in California, where the populist flamethrower keynoted the Friday evening dinner of the state GOP's fall convention, ticket sales were brisk. Jim Brulte, the California GOP chairman, said dinner tickets sold out — twice.

"We had to keep asking the hotel to allow more seats," he said in an email exchange. Bannon's speech also garnered national news coverage, which would have been unlikely with a typical political figure.

Bannon's revolution hasn't been flawless.

Despite backing the winning candidate in a special election GOP primary runoff in Alabama, where retired judge Roy Moore defeated the McConnell-endorsed appointed Sen. Luther Strange, Bannon's ability to topple other incumbents is unclear.

In Arizona, Bannon is supporting Kelli Ward in the Republican primary against Sen. Jeff Flake. Ward recently experienced campaign staff defections. Her past performance as a candidate was unsteady. In Nevada, Bannon appears to be relying on five-time loser Danny Tarkanian to oust Sen. Dean Heller in the primary.

Meanwhile, Bannon's insurgency also is relying on Republican primary candidates with establishment backing, with no evidence that these individuals would vote against Congressional leaders if elected, granted they might be more conservative than the alternative.

Still, Bannon is becoming enough of a force that at least one Republican primary candidate, for the Senate nomination in Wisconsin, bragged in a email fundraising appeal that he had won the "Bannon primary."

"The Steve Bannon primary in Wisconsin is over, and Kevin Nicholson has won, the Milwaukee Journal Sentinel declared," the candidate's email appeal said. A photograph of Bannon is featured prominently in the email.

Some Republicans, while not dismissing Bannon, say that he is beginning to fill the role of anti-establishment figures on the Right who often spoke at local GOP events in the past.

That he is organizing a concerted rebellion rather than just fomenting discontent through the media — and that he has a Republican president's ear, and general support, is unusual. But that some Republican want to hear such a voice is not.

"There is an audience for this among a segment of party activists," said Doug Heye, a GOP strategist who previously worked for the Republican National Committee.