Stephen Bannon, the former White House chief strategist and current chair of the conservative website Breitbart, threatened Monday to back primary challengers to every Republican senator who is up for re-election in 2018, save Sen. Ted Cruz (R-TX).

“That’s why I left the White House—remember, I said I’m going after the Republican establishment,” Bannon told Sean Hannity during an interview on Fox News. “And we’re going to go after them.”

Bannon has pledged to launch a self-described “war” against Republicans who aren’t loyal to President Trump. And there are apparently few people off-limits. The nationalist firebrand listed GOP senators all across the country—even those who have been supportive of Trump and his agenda—as targets for potential primaries, including Sens. Orrin Hatch (R-UT), Roger Wicker (R-MS), John Barrasso (R-WY), and Deb Fischer (R-NE).

“There’s a coalition coming together that’s going to challenge every Republican incumbent except for Ted Cruz,” he said. “We are declaring war on the Republican establishment that does not back the agenda Trump ran on.… Nobody is safe. We’re coming after all of them. And we’re going to win.”

Primary threats are not uncommon for party activists to make. It’s unprecedented, however, for a person so closely associated with a sitting president to threaten to target virtually an entire political party. That Cruz is the lone exception is notable, too. The Texas Republican has always been a darling of the conservative movement. But he went hard against Trump last year in the heat of the primary campaign, and refused to explicitly endorse Trump when he had a prime speaking slot at the Republican convention.

During his conversation with Hannity, Bannon went after Sen. Bob Corker (R-TN) in particular, who is locked in a bitter feud with President Trump. While Corker is not seeking re-election next year, Bannon said the Senate Foreign Relations Committee chairman should resign if he “had any honor or decency.” Once an ally of the president, Corker told The New York Times on Sunday that Trump might be setting the country “on the path to World War III.”

Bannon and other top Trump allies have expressed frustration with Senate Republicans in recent months, in particular over the multiple failed attempts to repeal and replace Obamacare. Bannon’s threat on Monday may be an attempt to try and hold the party in line behind Trump’s agenda as some feel tempted to follow Corker’s lead in airing their concerns about the president publicly.

“When you want to talk about why there’s no repeal-and-replace, why there’s no tax cut, why there’s no tax reform, why there’s no infrastructure bill, you saw it right there,” Bannon said. “[Senate Majority Leader Mitch] McConnell and Corker and that entire clique—establishment, globalist clique—on Capitol Hill have to go.”

Bannon’s threats don’t come without significant political risks. With only a slim majority of 52 seats in the Senate, going to war against Corker and other potentially vulnerable incumbents up for re-election next year could backfire. Just as was the case with health care, Republicans can’t afford to lose more than two of their own when they begin tackling the next agenda item, tax reform, or as they consider nominees for the open slots in Trump’s cabinet.