The self-ravaging of his credibility means Labour now has to abandon its strategy of trying to paint John Key and National as corrupt. To carry on in that fashion would be the height of hypocrisy.
But the bigger question now is whether Cunliffe can lead Labour into the coming election campaign with this albatross reeking around his neck.
Unless Cunliffe can come up with a very good explanation, the answer has to be 'no'. After all Cunliffe is not just trying to win the election, he is also auditioning for the job of Prime Minister. And on that score, today's events qualify as a fail - and by a wide margin.
The only relatively good news for his colleagues - if you can call it good news - is that under Labour Party rules dealing with emergency situations close to an election, the ballot on a replacement is likely to be restricted to the parliamentary wing rather than also taking in the wider party membership and affiliated trade unions.
Labour cannot afford spending a month consumed with choosing another leader - the length of time that would be needed for a party-wide vote on a successor.
But - with Labour already staring down the barrel of defeat for the third election in a row - who in their right mind would want the job now?
Debate on this article is now closed.