Speculation has escalated that John Bolton, the former UN Ambassador under George W. Bush and one of the country’s leading consummate foreign policy hawks, is poised to replace H.R. McMaster as President Trump’s National Security Advisor — as Trump reportedly considers upending his cabinet in the wake of Secretary of State Rex Tillerson’s dismissal Tuesday. Bolton had met with Trump at the White House on March 6. Just two weeks prior, at a public address at the Daniel Morgan Graduate School of National Security in Washington D.C., Bolton denounced a pillar of Trump’s foreign policy vision as “delusional.”

Bolton lamented in the February 21 remarks that Russian president Vladimir Putin has “not yet met effective opposition” in part because “America doesn’t have a coherent strategy… to deal with Russia.” He further observed that “Russian penetration of the Middle East” had been enabled in part by the Trump administration’s inaction. “I don’t think the administration has dealt strategically with the Middle East,” Bolton said. And in his most pointed criticism, Bolton added, “The notion that the Russians can help us with terrorism, I think, is ultimately delusional.”

Bolton has made similar, if less sharply critical, comments in the past; on a March 26, 2017, appearance on Fox News, he said it would be “be difficult if not impossible for the United States to cooperate with Russia on counter-terrorism measures.”

Forging counter-terrorism cooperation with Russia was one of the hallmarks of the foreign policy agenda Trump espoused during the 2016 presidential campaign. As far back as September 2015, Trump famously declared: “If you look at Syria. Russia wants to get rid of ISIS. We want to get rid of ISIS. Maybe let Russia do it. Let ’em get rid of ISIS. What the hell do we care?” And while in office, Trump has continued President Barack Obama’s information-sharing and military partnership with Russia in Syria, and personally discussed counter-terrorism issues with Putin.

“I think the Administration made a mistake at the beginning by continuing to follow the Obama Administration’s approach to dealing with ISIS,” Bolton said at the February event.

If Bolton were to become national security advisor, this plank of Trump’s agenda could be in for a major overhaul.