“Are people really discussing Boris Johnson as possible candidate for PM?” the tweet from 2012 says. “When I lived in London he was known as the gaffe man!”
The message appeared to have received little attention before Saturday, but is now being widely retweeted by critics of Mr Johnson, who was London mayor at the time of the tweet.
“Can we please work out some kind of compassionate scheme for Brits looking to escape to NZ and competent, empathetic leadership please?” one UK user responded on Saturday to Ms Ardern, who lived in the UK after being hired in 2006 as a policy adviser in Tony Blair’s Cabinet Office.
Another tweeted: “She was spot on even then!”
Ms Ardern, who was an opposition MP in 2012, has garnered global acclaim for her national leadership amid the coronavirus pandemic, which has led to just 25 deaths in the country and around 2,000 cases.
The 40-year-old’s reward was a landslide election victory on Saturday, likely allowing her to form the first single-party government there in decades.
In a speech, Ms Ardern said: “Tonight New Zealand has shown the Labour party its biggest support in 50 years.”
“We have seen that support in urban seats and rural seats and seats we may not have expected. And to that I have only two words: Thank you.”
Mr Johnson, on the other hand, is widely viewed as having led a much more haphazard response to the pandemic, which has culminated in more than 43,000 coronavirus-related deaths in the UK so far.
Mr Johnson also contracted the virus himself earlier this year, and is under increasing pressure within a Conservative Party disillusioned with his leadership and struggling poll ratings.
On Saturday he congratulated his New Zealand counterpart on her win.
“Congratulations [Jacinda Ardern] for winning a second term as New Zealand PM,” he tweeted. “From our work together to tackle climate change to forging an exciting new trade partnership, the UK and NZ have great things to look forward to in the future.”
