Gov. Bruce Rauner’s trusted policy chief kicked off another week of tumult in the administration on Monday, becoming the latest high-level staffer to leave the governor’s staff under protest.

And signaling that the turmoil is far from over, another five senior staff members quickly followed Mike Mahoney out the door before the day was over.

A new hire — a hand-picked assistant whose first day on the job was Monday — was also fired based on homophobic and racially insensitive tweets.

That brings the total administration exits since last week to at least 20.

Fear is the operative emotion in the governor’s office, which has essentially been taken over by a conservative think tank, according to remaining staffers. The resignations on the administration’s policy, digital and communications team, were a way to protest the new ideology, sources said.

“People are scared,” a staffer said Monday. “I was cornered by a staffer today so worried she’s going to be fired. She has a ‘meeting’ with [new chief of staff] Kristina [Rasmussen] and was visibly upset.”

Mahoney, who served as the governor’s chief of staff for policy and legislative affairs, resigned on Monday. Bridget Davidson, the governor’s digital director; Bob Stefanski, director of House and Senate Operations, and Deputy Press Secretary Olivia Munson, also stepped down.

Sources said the governor’s team in Washington, D.C., including Kathy Lydon and Therese Magnuson also resigned.

“They are dropping like flies,” a Rauner staffer said Monday.

Phil Rodriguez, who served as deputy chief of staff for public engagement, also quit, but he was allowed to move to another job.

Mahoney was replaced last week by Michael Lucci, policy director for the Illinois Policy Institute, the state’s leading conservative think tank. Mahoney had been given an option to stay on in a different role. Mahoney, who at one point served as Rauner’s pension expert, helped to craft the Tier 3 pension plan that ultimately passed both chambers. The Joliet native was also known as the governor’s “social chair,” organizing events with the governor and lawmakers.

Illinois House Republican Leader Jim Durkin called Mahoney “the foremost expert on pension and pension reform in Springfield.”

The administration shakeup began on July 10 when Rauner unexpectedly fired his chief of staff, Richard Goldberg, whom sources described as “the most loyal and unified soldier who carried out his [Rauner’s] every last wish to his very last day.” Goldberg was swiftly replaced by Rasmussen, former president and CEO of the Illinois Policy Institute.

The shift came after Rauner vetoed a state budget that included an income-tax hike, only to see his veto overridden with the help of several Republicans.

Many political insiders believed Rauner would be able to use his anti-tax stance to carry him through his re-election. But the governor surprised observers when he quickly replaced most of the moderate Republican staff that helped him craft that message with members of the think tank, which had just been slamming him for being too willing to compromise with Democrats.

While many are still scratching their heads over the takeover, a source with close knowledge of the governor’s administration said the uproar was sparked by Rauner’s and his wife’s “unhealthy obsession with media and messaging” and discussions the couple had at “North Shore cocktail parties.”

“They had conversations with people at these parties who said ‘I had no idea you were doing this.’ It would blow up the whole week’s plans,” the source said.

Speaking of the state’s first lady, the source said: “I think her footprint on decision making, on his decision making, is larger than most believe.”

The source, too, said the Illinois Policy Institute’s current CEO John Tillman “clearly has the ultimate influence [on the governor] at this point.”