A series of mini-scandals have failed to touch the sides. Support for the government surged four points in the latest Herald Digipoll.
Labour sank six points to 29.5%.
Leader David Cunliffe crashed a similar amount to 11.1% - worse than the worst rating of his pedecessor, David Shearer.
The poll would allow National to govern alone. It's headline results:
National: 50.8 (Dec 2013: 46.8)
Labour: 29.5 (35.4)
Greens: 13.1 (10.8)
NZ First: 3.6 (3.9)
Conservative: 1.3 (1.3)
ACT: 0.8 (0)
The brouhaha over an Antoine's fundraiser did not dent the PM. John Key's preferred Prime Minister rating rose 4.6 points to 66.5% - close to his all-time high of 70% during National's first term.
"It's not a great poll," Mr Cunliffe said on TVNZ's Breakfast.
"But we're already on the front foot," he said over Judith Collins and what he called "crony capitalism" (the poll would have captured part of the reaction to the PM ticking off Ms Collins on March 12 after she initially failed to fully inform his office of all events around the Oravida controversy).
"There's only one poll that counts," the Labour leader said, falling on the old chestnut.
The poll of 750 eligible voters was conducted between March 6 and March 16. The party vote figures are of decided voters only.