Steve Bannon has pledged to put forth candidates to challenge six of the seven incumbent GOP senators in 2018, provoking fear that the party will suffer avoidable losses.

The GOP establishment is furious and fearful of Bannon's vow to blow up the party establishment.

While some think Bannon is on a mission to repair his personal image and boost his power, others say he remains a devoted loyalist of President Donald Trump who is intent on remaking the party in the president's image.

Steve Bannon, President Donald Trump's former campaign manager and top White House strategist, is on a mission to blow up the Republican Party.

While Bannon, who left the White House in August, claims to be fighting for Trump and the West Wing's agenda, his pledge to challenge every incumbent GOP senator — save for Texas Sen. Ted Cruz — in the 2018 midterm elections may well empower Democrats in competitive races, leading to avoidable GOP losses.

Following a chaotic seven months in a White House defined by infighting and few substantial achievements, Bannon has attempted to reassert influence over the direction of the administration and the Republican Party more broadly.

On Monday, he told Fox News host Sean Hannity that he is "declaring war on the Republican establishment" in an effort to promote GOP leaders loyal to the populist, nationalist platform Trump campaigned on.

And Bannon has just two requirements for these candidates: They must disavow Senate Majority Leader Mitch McConnell and they must vote to end the Senate filibuster.

'Nobody's safe': GOP senators under fire

Bannon has vowed to back right-wing challengers to six Republican incumbents up for reelection in 2018. And he scored his first victory when right-wing candidate Roy Moore beat GOP incumbent Sen. Luther Strange, who was endorsed by Trump, in Alabama's September primary runoff for the Senate seat Jeff Sessions left when he became attorney general.

While all of the incumbents have voted with Trump at least 90% of the time, Bannon claims that the "establishment globalist clique on Capitol Hill" has "total contempt for the forgotten man," or the white working class voters Trump purports to be fighting for.

"Even safe incumbents like Barrasso and Deb Fischer, they have to understand something — just voting is not good enough, you have to have a sense of urgency," Bannon told Hannity on Monday, referring to Wyoming Sen. John Barrasso and Nebraska Sen. Deb Fischer.

"Nobody's safe, we're coming after all of them, and we're gonna win," he said.

In Nevada and Arizona, where Sen. Dean Heller and Sen. Jeff Flake, respectively, are widely viewed as the most vulnerable GOP incumbents, primary challengers have already announced their bids. Kelli Ward, a former Arizona state senator who was unofficially endorsed by Trump, has raised more than $1 million so far in 2017, while in Nevada, Danny Tarkanian, an independently wealthy businessman, is polling well among primary voters, more than half of whom say they'll vote for someone besides Heller.

'Strategically suicidal'

The GOP establishment is both furious and fearful of Bannon's organized attack and are warning that the party must take his threats seriously.

Matt Mackowiak, a GOP strategist and president of the Potomac Strategy Group, told Business Insider that Bannon's plan may well leave the GOP with devastating losses in key states, while diverting needed resources from races against vulnerable Democrats.

"We have limited resources. Where are they gonna go? Are they going to go to try to shore up establishment senators in red seats in red states?" he asked. "That is strategically insane. That is strategically suicidal. We ought to be spending 95% of our money on the five most competitive US Senate races next cycle."

Indeed, Bannon alleges that top GOP donors are abandoning McConnell and the establishment, opting to fund his efforts instead.

"Karl Rove, Steven Law, these guys should get the joke," Bannon told Hannity, referring to top GOP operatives. "Their donors are coming to us because they are tired of having their money burned up by trying to destroy people like Judge Moore. There's a new game in town."

Others on team Trump argue that there's plenty of money to go around.

"I've never known a Senate race to lose for lack of resources," Ed Brookover, a former senior adviser to Trump's transition and a partner at a DC public affairs firm, told Business Insider. "I don't have a concern about the primaries draining the budgets of conservative and Republican organizations."

Bannon's most prominent benefactors are the Mercer family — billionaire hedge fund manager Robert Mercer and his daughter, Rebekah Mercer, who have poured tens of millions of dollars into conservative politics and funded Cruz's 2016 presidential campaign before turning their support over to Trump.

Challenging Cruz is likely off the table in part because of the senator's close relationship with the Mercers.

While it's unlikely that more than a few of the primary challengers will upset their incumbent opponents, these races may leave Democrats in a stronger position in competitive states like Arizona and Nevada.

An 'irresponsible populist cowboy'

Some mainstream Republicans argue that Bannon, who resumed his job as head of the right-wing Breitbart News after leaving the White House, is on a personal mission to repair his image and boost his power to the detriment of the Trump presidency and the party.

"I think he's trying to mask his failure inside the White House and blame others for his seven months being effectively fruitless, certainly legislatively fruitless," Mackowiak said, calling Bannon "a net negative" in the West Wing who was incapable of negotiating on Capitol Hill. "We have one irresponsible populist cowboy that's threatening to blow the whole thing up for his own reasons and I think that is deeply irresponsible, strategically unwise, and that threat is very real."

Others say Bannon is, in fact, being strategic, given that his stated goal is to effectively recreate the GOP in Trump's image.

"There's already a fracture within the GOP, but it's not a clean break yet," Reed Galen, a GOP consultant and deputy campaign manager for Sen. John McCain's 2008 presidential campaign, told Business Insider. "I think he is looking to make as jagged a break and as ugly a break as he can between what he sees as the nationalist, nativist Trump wing and the establishment, whatever's left of Rockefeller Republicans."

Bannon's risky approach may stem from his fatalistic view of the Trump administration, which he reportedly predicts won't make it to 2020. Behind closed doors, Bannon has reportedly argued that Trump has a 30% chance of completing his first term and that his own cabinet and vice president will eventually force him out of office.

Whether or not Bannon is successful in remaking the Republican Party, in the short term Democrats are poised to benefit from the party's disunity.

"A fractious, bloody, nasty, expensive civil war within the Republican Party next year benefits the Democratic Party," Mackowiak said. "The only people cheering are Democrats, they're absolutely thrilled to death."