All of this at age 41.
But earlier this year, he announced he was stepping away from politics, a decision that shocked many but one that he had mapped out some time ago.
In an interview with the Chronicle last week, Mr Power said he was leaving with few regrets.
"You kind of take it as it comes, and you get very focused on doing things for individuals in your electorate, and that's part of the job the national media, especially, don't write about. But it's work that's extraordinarily significant," he said.
"Some of the best letters I've had have come since I announced I was going to stand down, and they've come from people I have helped during my 12 years as MP."
In hindsight, Mr Power said he might have been a bit better organised earlier on in his political career, saying he was "a bit manic", charging around one of the biggest electorates in the country.
"But with a majority of 289 votes you're very focused, being everywhere for everything."
He was soon singled out for bigger things with the media picking him out as a star on the rise.
Timing is everything, and he arrived in Wellington at a time the National Party "tide" was going out. He moved to the front benches very quickly.
"Politicians are divided into three types: the 'campaigners' who love being out there selling the message; the 'operatives' who like the dark arts and machinations of politics; and then there are the 'policy wonks' and that's what I am.
"I've always enjoyed the ideas and pushing agendas and debating issues," Mr Power said.
In 12 years, Mr Power has fashioned an amazing record in terms of legislative success, especially in his justice portfolio. He's overseen major reforms to the criminal justice sector and liquor laws. He has also undertaken lower-profile reforms of the commerce sector, including changes to financial market rules.
"There are things I would like to have finished. One of them was the Alcohol Reform Bill, and the other has been the work around child witnesses in the court system, which is really important to me," he said.
He regards some of the processes in our court system as "barbaric".
"The way the court system treats children and vulnerable people, as both victims and witnesses, is one of them.
"I don't think the adversarial system, which our entire justice system is based on, serves those people well. I think they should be able to give their evidence in court early on, have it videotaped, leave the court and never have to face it again, and get on with their lives."
Mr Power's ideas had been formed earlier, but a visit to Austria and Germany a couple of years ago coalesced everything.
"I saw how this model worked in those places and was very impressed. I came back and told the Prime Minister we had to do this. He's been hugely supportive of it since then," Mr Power said.
"This is not a criticism of lawyers or judges but the way the system rebrutalises these victims, when they've already been through something through no fault of their own. I had an obligation to fix that, and I've started that process," he said.
"If there's one regret, it's that I don't get the chance to finish that. But there'll be some announcements around this topic in the very near future," he said.
Pushing legislation through requires planning, and that success had its birth during National's last two years in opposition.
"I was going around the bend because it's so negative and so entrenched in opposition. Your ability to shift things is basically nil," Mr Power said.
"We started to put a plan together of what our first term in office might look like, not because we thought we'd win but because, frankly, to do anything other than that was driving us nuts."
Once in power in 2008, the party was ready.
"Lawyers will always tell you the art is 90 per cent preparation and 10 per cent execution. So when we were ready to go, I knew exactly what I wanted to have happen all the way through."
He reckons about 35 new laws have been enacted during his watch in the past 34 months. How did this happen, in a place where legislation sometimes never gets past first base?
He said it was because the Prime Minister gave him plenty of rope.
He also became convinced that the broader the consensus you could get on issues, the more likely Parliament was to take a favourable view of it.
"The gem I've taken out of the last 12 years is: don't be afraid to admit when you've got something wrong, to compromise and to get a result that covers as broad a section of Parliament as possible."
What of his life after politics?
"I haven't said publicly what I'll be doing, but I always said I wanted to go into the private sector in a commercial role, because I've done a lot of work in the financial markets over the last three years.
"It's about not being afraid to put your hand up at 41 and say, 'I'll learn some new things'."
Mr Power understands not every politician knows when it's time to leave Parliament, but "I've had a plan for how long I was going to do this before I was first elected, and I never wavered from it".
"But it's not how long you serve, it's what you do when you're there that matters. I would rather be remembered as someone who got on and did things."
As for his leader he says John Key had brought a "very natural way" to governance.
"It's not forced or dictatorial in any shape or form. He's very consensus-driven. He'll get his 'kitchen cabinet' (Bill English, Gerry Brownlee, Steven Joyce and Mr Power) together and asks for our views. He'll listen and then say, 'This is what we're doing'," Mr Power said,.
But he said it was a model of governance the public sector, especially, found very difficult to deal with. It was a lot different from what was happening over the nine years of the previous government.
Despite his key position in the Cabinet, his thoughts rarely stray far from his Rangitikei electorate.
There isn't a traffic light between Tokomaru, at the southern end of it, and Taumarunui, to the far north. Yet in the last four elections the voters have seen fit to elect a city lawyer whose politics are not particularly conservative, and who is regarded as the liberal in the party.
But it's something that he says he's humbled by.
"Because, in the end, they've said that they may not agree with everything I've done or said, but they trust my judgment. They've been remarkably forgiving."
