Prime Minister Bill English is downplaying the impact of Peter Dunne's resignation on National's re-election chances.
Dunne, the United Future leader and MP for Ohariu, announced his shock resignation this afternoon just weeks before the general election.
National has already directed its supporters to vote for Dunne, and its candidate Brett Hudson has included this message on his campaign leaflets.
English denied that this put National in an awkward position, saying that it was easier to correct "one letter in one electorate" than change billboards across the country as Opposition parties had done in recent weeks.
"It's not a circus. Peter Dunne's made an unexpected decision, Brett Hudson is a well-known candidate, and he'll be fighting hard to win that seat."
He was not worried about the loss of a support partner, saying National still "had a lot of voters".
The National Party had no influence on Dunne's decision, English said.
He's made his own decision. We certainly didn't give him advice."
Asked whether he wished Dunne quit earlier, he said "at least we don't have to change every billboard in the country as both the Greens and Labour have set out to do and haven't yet managed".
Hudson said this afternoon that he would now run a full "two ticks" campaign.
"Many people have told me that they have long wanted to vote for their National candidate as well. I am very proud to now be able to seek both their votes."
Dunne is quitting politics at the election, in a shock announcement made today.
Dunne cited recent polling for his decision to quit politics after more than three decades.
In the latest twist to a chaotic election, Dunne is the third leader in just three weeks to resign, following Labour's Andrew Little and the Greens' Metiria Turei.
Dunne's departure is undoubtedly a blow for National, which has relied on his vote in Parliament to help achieve a majority.
The Ohariu MP said the current political environment is "extremely volatile and unpredictable".
"However, I have concluded, based on recent polling, and other soundings I have been taking over the last few weeks, that, the volatility and uncertainty notwithstanding, there is now a mood amongst Ohariu voters for a change of MP, which is unlikely to alter."
Dunne has been an MP for 33 years. He was facing a serious challenge in Ohariu from Labour's Greg O'Connor, the former Police Association president.
O'Connor paid tribute to Dunne, saying he had been a "very, very effective local MP" who had been loyal to Ohariu.
"Yes, it's a surprise," O'Connor told the Herald.
"But this is an election like no other."
O'Connor said Dunne's resignation did not change his campaign.
"I've still got a lot of work to do. It certainly doesn't mean that the seat becomes any easier."
Labour leader Jacinda Ardern acknowledged Dunne's long service as an MP.
She said O'Connor was a strong candidate and would continue to work hard: "This race just got very, very interesting. It was already interesting but certainly it will be one to watch."
Ardern said it was hard to determine whether winning the seat would be a harder job as a head-to-head with National's Brett Hudson.
It was not known whose Dunne's supporters would rally behind, she said.
"Greg is working hard earning every single vote."
She said some of the Ohariu candidates would have to change tack "given some of their past messaging" - a reference to the fact that Hudson had told supporters to vote for Dunne in his campaign leaflets.
Prime Minister Bill English said he respected Dunne's decision.
"Now we have a clear choice in Ohariu between National's Brett Hudson and the Labour candidate."
He thanked Dunne for his contribution to the National-led Government over the last nine years.
"In the last three elections National has won the party vote in Ohariu by a significant margin. We will now fight hard to win the seat as well as maximising our party vote in the electorate."
English had previously explicitly told National voters to give their candidate vote to Dunne rather than National's candidate Hudson.
Dunne said he had decided it was time to stand aside: "After much consideration and discussion with those closest to me, I am announcing today that I will not be putting forward my nomination for election to the next Parliament. I do so with considerable reluctance, but I have always understood that holding public office is a temporary privilege granted by the people, and can never be taken for granted.
"I have thoroughly enjoyed serving the Ohariu electorate in its various forms since 1984. I thank my constituents, my supporters, my party, and all those staff members who have worked so loyally and professionally alongside me over the years, but above all, I pay huge thanks to my wife Jennifer, my sons, James and Alastair, raised in the heat of politics, and my entire family for their loyal support, patience and encouragement for so long.
"I am especially proud to have worked alongside successive National and Labour-led governments in the collaborative environment of MMP, and to have had the privilege of serving as first an Under-Secretary and then a Minister under seven different Prime Ministers for just on fifteen years. I am very proud of the many changes I have been able to make in my portfolios over the years to make New Zealand a better place in which to live and raise a family."
Dunne said he made his decision with "considerable reluctance".
"But I have always understood that holding public office is a temporary privilege granted by the people, and can never be taken for granted."
Dunne said Ohariu had been a "very large part of my life" and he has raised his family there. Representing the electorate had been "an absolute delight".
"But good things cannot last forever. Now it is time for me to put all that behind me, take the election hoardings down, say goodbye to Parliament without bitterness or regret, and get on with life."
In a recent profile for the Herald, he said at age 63 he had occasionally considered retirement, but still enjoys "the buzz of involvement" and in particular the chance to help people.
"I look around and think, 'if I wasn't doing this, what could I do to replace that?' "And I haven't found an answer yet."
Act leader David Seymour tweeted Dunne was a "symbol and enabler of how our major parties drift with no real agenda", and had enjoyed ministerial cars and perks when the housing crisis began under Helen Clark and continued under National.
"He has been swept out by the tidal change against do-nothing politics," Seymour wrote.
Green Party leader James Shaw said he had a great deal of respect for Dunne, who had had a long and distinguished career.
"My sense of it is that he could sense there is a change of Government coming up and at this point in his career he didn't want to go into opposition."
Shaw also believed the Greens' decision to stand aside for Labour's Greg O'Connor in the seat played a part, but the final nail in the coffin for the United Future MP was him looking at how the election was going.