But it's what the self-made millionaire who grew up in a state house does next that will determine his place in history.
And as the 38th Prime Minister of New Zealand prepares for a third successive term in office - just the eighth politician to do so - University of Auckland politics and international relations associate professor Jennifer Lees-Marshment warns Key's greatest enemy lies within.
She said complacency and arrogance could lead to the eventual downfall of the party and Key needed to address this early. It was important to acknowledge shortcomings that resulted in ministerial resignations - most notably Judith Collins' - and avoid any repetition.
"He could just carry on, not addressing the underlying weaknesses or doing much different, and just enjoy the luxury of a win against a weak opposition before his government inevitably descends into arrogance as most - if not all - third-term governments do," said Lees-Marshment.
"Plodding is fine, and in a global financial crisis [this] may be all that is achievable, but if we are - as National claimed in the campaign - now doing so well, now is the time to change pace and move forward in more exciting directions."
She said everyone "would give him credit for steering NZ relatively unscathed" through the global financial crisis, a crippling four-year period.
Key's biographer, John Roughan, assistant editor of the New Zealand Herald, agreed but said it was important to remember the surplus National inherited from Labour meant they were in a strong position to weather the financial maelstrom.
Lees-Marshment said another plank of Key's success was his confidence leading a Cabinet of strong personalities. Unlike previous prime ministers Key was not threatened by other able politicians working with him, which was important for ongoing success for National.
"His leadership is not about himself, but others."
He had also won over the public with a unique, informal communication style.
Said Lees-Marshment: "He has very carefully branded a positive relationship between himself and New Zealanders which is reflected in his personal standing in the polls during recent controversy."
He had also taken a personal interest in the Christchurch earthquake and made a point of being involved from the outset of the disaster.
Roughan said one of the highpoints of Key's tenure was joining political forces with the Maori Party.
In the lead-up to the election there was speculation Key might resign part-way through a third term. But this week he indicated he would stay on. But would he take a tilt at becoming just the third man to win four successive terms as Prime Minister? Time will tell.
- By Lynley Bilby of the Herald on Sunday
