"There's an old political saying, 'As Labor as Cessnock'," Cain said.

"It's like, is the Pope Catholic? Everyone just voted Labor. It was just assumed that you voted Labor."

So how did the kid from the Labor heartland end up a member of the Liberal Party, and now one elected to represent the party in the ACT Legislative Assembly?

It started with him watching and listening to Australia's longest-serving prime minister Robert Menzies, a person and political leader Cain said was "like someone I had never met before".

Cain had always had a libertarian streak in him, so the notion that a Liberal could speak and vote and according to their conscious sat comfortably.

His quiet passion for free and open debate - and a fear it was being curtailed in public life - would be among the factors that would ultimately push a proudly apolitical public servant, and father of seven, into politics.

"I just saw a decline in the quality of public debate, I just couldn't put it in any other way," he said.

"[I had] a growing concern that free and open discussion seemed to be discouraged rather than encouraged. which is really how you build up your best policies and best ideas."

The Canberra Times spoke to Cain for its series profiling the eight new members voted into the ACT Legislative Assembly at last October's election.

Cain was involved in one of the election's closest contests, narrowly defeating then Labor Attorney-General Gordon Ramsay by just 160 votes to win a seat in the Belconnen-based electorate of Ginninderra.

He has promised to make those constituents, and the issues affecting them, his number priority in parliament.

"I'm an elected official with a responsibility to the people who put me into office," he said. "I'm thrilled to be part of the Liberal team, but my primary responsibility is to the electorate."

Cain was born into a working-class family, moving homes multiple times as his father bounced in and out of a job. His family eventually settled in a part of West Cessnock which Cain referred to as the "migrant village", an estate primarily for new arrivals.

After stints as a mathematics teacher in NSW, and then as a school principal in SA and Canberra, Cain headed back to university to study law.

He was accepted into the ACT government's public service graduate program, where he was placed in the territory's revenue office.

Cain rose up the ranks, eventually put in charge of the office's tax disputes unit in 2011. He became involved with the ACT Law Society, serving as a vice-president and chair of its government law committee.

In 2012, Cain said he was appointed to an expert committee to provide legal advice on the rollout of the ACT government's 20-year reform of the tax system - a policy the Canberra Liberals have stridently opposed.

As a lifelong Liberal voter (though not, at that stage, a party member), did Cain feel unease about Labor's plan?

No, he said. Not at all.

"I had a service mentality. It sounds very pious, but I really tried to encourage it as much as I can."

Cain hadn't contemplated a career in politics until a colleague's brief comment at an ACT Law Society lunch just months out from the 2016 ACT election.

"If the Liberals don't get elected this time," Cain remembered the colleague telling him, "they never will".

"For some reason that I cannot explain, that lodged on the hard drive ... so to speak," Cain said.

"I thought yeah, they should win, shouldn't they?"

The Liberals didn't win.

But for Peter Cain, the spark had been lit.