Elliott, who has held the titles of senior counselor and deputy chief of staff, is an inside operator who has grown increasingly comfortable with publicly addressing Newsom’s greatest challenges. He did so frequently as the governor’s housing and homelessness czar — punishing cities that fall short on housing and then recently extending that same accountability to cities on homelessness.

His measured commentary on regulating artificial intelligence and balancing the state budget is carefully parsed by lawmakers and the Third House at the Capitol for clues on how Newsom might come down on hundreds of bills and billions of dollars in spending.

Newsom praised Elliott, referring to his longtime aide as “my Swiss Army knife.” The governor lauded his strategic insight, political acumen and commitment to the state.

“He has served in innumerable capacities for over a decade — my most senior advisor on housing and homelessness, an expert on technology and artificial intelligence, a trusted campaign advisor, and most importantly, a loyal friend,” Newsom said in a statement, adding he was excited to see Elliott turn to new opportunities.

Reflecting on Newsom’s 2020 State of the State speech, which he had a hand in writing and that laid out major planned initiatives, Elliott said he was proud to have been a part of the state’s efforts to address mental health problems, namely through the recent narrow passage of Proposition 1 in March, as well as the CARE Court program.

But Elliott acknowledged the administration still has its hands full in implementing the wide swath of far-reaching social service initiatives instituted under his watch.

“I feel very confident that the pieces are in place. I’m optimistic about that, and I’m not leaving anything halfway done,” he said. “But now look, implementation is a challenge.”

Elliott has faced his own challenges over his career, serving two mayors after the sudden death of his boss, San Francisco Mayor Ed Lee in 2017. Outside of that work, he spent much of his career with Newsom — including being part of the faithful few who were there for his last days at City Hall and his aborted campaign for governor in 2009.

Beyond having policy tentacles that reach across — and outside — the administration, Elliott is regarded internally as a top “Newsomologist” — anticipating probing questions and demands from a governor who prides himself on being able to see around political and policy corners.

Jason Kinney, another fixture in Newsom’s orbit, said Elliott could go deep in the weeds with the governor during brainstorming sessions “without getting mental whiplash.”

“Sometimes, it was like watching Kasparov versus the IBM Supercomputer — they made each other better,” he said.

Part of his skill is translating dense policy prescriptions into layman’s terms and then leaning into his history with Newsom to personalize the pitch. After Newsom unveiled his slogan for Proposition 1, which was “Treatment Not Tents,” a POLITICO reporter reached out to another adviser to ask if the slogan was a tribute to Newsom’s San Francisco homelessness program from 2002, which was dubbed “Care Not Cash.”

“That was Jason,” the adviser said at the time, showing “grudging respect for the policy guy.”

In a fact-check of the anecdote, Elliott refused to take credit, attributing the slogan to Newsom political consultants Ace Smith and Brian Brokaw.

Friends inside and out of the administration joke that all his years at Newsom’s side have rubbed off in manifest ways, with Elliott by turns adopting some of Newsom’s mannerisms, and, on occasion, his trademark vocabulary and affection for alliteration.

Dana Williamson, Newsom’s chief of staff, pointed to another famous figure, fondly comparing Elliott’s office etiquette to the fictional character Kramer on the 1990s sitcom “Seinfeld.”

“He barges into the room, starts talking, and doesn’t care what’s going on,” she said. “I will miss him dearly.”

But jobs with ambitious elected officials are notoriously all-engrossing, and Newsom is known to over-prepare even for brief statements, making the work both challenging and taxing. Elliott spoke to the grueling nature of his positions, though he was quick to note that many other people have it much tougher. (He’s not laboring on an oil rig.)

“It’s never easy to leave jobs like that, but he accomplished everything he set out to do both in terms of policy and being one of Newsom’s top people,” said Jim DeBoo, a former chief of staff to Newsom.

While he’s leaving the state job, Elliott expects to remain in Newsom’s inner circle and said they have already been thinking about ways to work together in his new capacity as an outside consultant. A Palo Alto native with degrees from Harvard Kennedy School and Columbia University, he is married to Nicole Elliott, director of the California Department of Cannabis Control. They have two children, aged 4 and 1.

Elliott said he looked forward to sitting out some issues that are compulsory for high-ranking aides in the governor’s office and instead focusing on those that most interest him.

“The curse and the blessing of this job is that you have to confront 1,000 issues, and you don’t get to pick them,” he said. “Now, I get to go focus on a smaller number of issues that I get to choose that I’m really passionate about.”

Elliott added: “I’m really excited to be a consistent pick-up and drop-off for my kids at school.”