He announced his shock resignation just weeks out from the previous general election.
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That left National scrambling, having already directed its supporters to give their electorate vote to Dunne, a message its candidate Brett Hudson had written on his campaign leaflets.
Hudson then had to do a 180 and run a full two ticks blue campaign at the last minute.
Reflecting on that situation three years ago, he says four and a half weeks out from election day wasn't enough time to win the seat.
"Had there been sufficiently more time for those National-leaning voters to have better got to understand me and what I was looking to achieve, then that result could well have been different and more in line with the party vote result."
Labour's Greg O'Connor snapped up the seat in 2017 with a 1051-strong majority over Hudson.
He says it will potentially be that close this time around.
"We're fighting for every vote again."
Earlier this year O'Connor announced he was running electorate only, making his bid for the seat all or nothing.
He says the main reason for that is because he enjoys the electorate work more and that's where his skillset lies.
Hudson, however, has a different answer to that question.
"There's only one thing I read into sitting MPs that go off the list… in each instance they do it because they don't like the number they're going to get."
But Hudson says he's in essentially the same situation, because he won't get into parliament as a list MP based on how his party is currently polling.
"Both of those gentlemen believe that they know all of the solutions for the electorate and I actually think that part of the job as a representative is to not think they know everything, but to actually make sure they talk to the constituents."
Hudson and O'Connor both agree housing and transport are big issues for Ōhāriu.
National has promised $900 million for constructing the Petone to Grenada Link Rd as part of a new Seaview to Grenada Link Road project.
Hudson says that will add resilience to the transport network, which has suffered serious congestion from slips on the road or accidents in the past 18 months.
"If they happen in the morning, the traffic comes to a complete standstill literally for hours.
"I can look outside my office window on the days that happens and see them standing still."
Both Hudson and O'Connor said the road would unlock the LincoInshire Farm area to build thousands of homes, which would ease growing pressure on the electorate.
Hudson says he has been fielding concerns about proposed densification in the suburbs through the council's draft spatial plan.
He says opening up the farm for housing would ease those worries.
O'Connor says residents wanting to downsize but stay in the area are struggling to buy, as well as those who have grown up there and want to secure their first home.
He says the recently released National Policy Statement on urban development allowing for six-storey builds would go a long way to solving the housing shortage.
"There are people who obviously don't want their own areas to change, but the important thing is to ensure there is good planning and the designs of the buildings are in keeping.
"That's what people's fear is, they fear a whole row of Stalinist buildings along the railway track. It is not going to be that."
The electorate also has one specific long-running issue that ironically central government MPs can do little about, but is a hot topic in the general election campaign regardless.
It's Johnsonville Mall.
Martin adequately describes the situation as "a particularly hairy little problem because it's privately owned".
Redevelopment plans for one of the saddest malls in the country were first proposed more than a decade ago, yet nothing has happened.
Located smack bang in the middle of Johnsonville, it should be a thriving hub for the electorate.
Martin concedes there's not really anything a local MP can do apart from to have conversations with stakeholders and foster a good relationship.
"You have the conversations, but you don't pass laws to get people to change their mall up."
Hudson says there was one "enormously big" lever central government could pull, which is compulsorily acquiring land for housing, but he wasn't advocating for that yet, if at all.
"The best thing that can be done about the mall, and I have done, is maintain a constructive relationship with Stride [the owner]."
O'Connor says he has also built a trusting relationship with Stride Property.
"It's not good enough to sit back and throw stones and as recently as last week I've spoken with the mall owners and ensuring we know what they're doing and how I can assist."
Among the things O'Connor points to having delivered this term is a business improvement district, which he says has given a voice to businesses outside Johnsonville Mall.
He's also proud of his advocacy around the Newlands fire station, which was put in jeopardy when Wellington City Council decided not to renew its lease.
O'Connor organised a public meeting and successfully lobbied for the fire station to remain in the area, rather than be relocated to Johnsonville.
But it was Martin in her capacity as Minister for Internal Affairs who arguably wielded the most power over the decision.
"I know, I was working on it for eight months. I just didn't pull a public meeting together."
In Martin's view the permanent solution for Newlands is an emergency services hub that includes Civil Defence and Wellington Free Ambulance.
The Opportunities Party candidate Jessica Hammond is making the case for new parties to get into parliament.
"First of all, voting for the National or Labour candidates won't make any difference to the make-up of parliament.
"If the people of Ōhāriu elect me, then we get a new party in parliament with some new fresh ideas, fresh energy and passion, and we could actually make a difference for this country."
Hammond is born in Wellington and works as a public servant.
She says there's a huge amount of unpaid work in the electorate done by stay-at-home parents and TOP's basic universal income would recognise that, as well as delivering a significant change to the welfare system.
Act's candidate Sean Fitzpatrick has lived in the electorate for about 40 years and is running for the party vote.
He says the middle class electorate will gain more individual control over their lives through the party's economic recovery plan, which includes scrapping the RMA and tax cuts.