Was National Party leader John Key using his position in 2002 as a freshly-minted member of Parliament to profit from share trading?
And if this is true, did he know at the time that he was in breach of Parliament's rules?
The Labour Party, principally through the agency of the deputy Prime Minister, Michael Cullen's, press office - no doubt with Dr Cullen's approval - claims both accusations are true, and that therefore Mr Key is a liar, having misled both Parliament and the public.
The accusation is an old one, revived for electioneering purposes.
Most recently it was raised by the Prime Minister in July during an acrimonious debate in the House when she accused Mr Key of personally profiting from the sale of New Zealand's railway network.
Mr Key denied it.
Parties are busy looking for mud to sling and Labour's researchers are no exception. They have been digging into the public records of Mr Key's share trading six years ago.
The records show Mr Key's family trust owned 50,000 Tranz Rail shares before he was elected.
Labour claims he asked numerous questions about Tranz Rail in 2003, without disclosing his family trust's holding, asked in April (but was refused) for commercial information about the company, bought 50,000 shares in his own name the following month; sold them in mid-June, followed a few days later by the sale of the family trust's shares.
Mr Key has said this week he never personally owned shares in Tranz Rail; his family trust did. His sharebroker managed the portfolio and was able to act without reference to the MP.
He had realised early in June 2003 that Tranz Rail was going to become a political issue, and had ordered the whole share parcel sold, which it was "at a loss".
Mr Key's comments amount to an admission of guilt and an expression of regret; it will be far worse for him and the National Party if more embarrassing disclosures emerge.
He agreed he did not make public details of his shareholdings and "in hindsight" should have.
He did not intend to mislead with regard to the number of shares "the family trust owned", and he now believes he should have instructed their sale earlier.
Whether people accept his word remains to be seen but Dr Cullen is making his best efforts to show an intent to mislead and his accusation and Mr Key's admission will generally work in favour of the Labour Party's present election stance of asking voters whom they should trust.
But that can work against Labour and others, and in the context of the Winston Peters affair few MPs emerge with any credit whatsoever.
The attitude of the Prime Minister, who sacked ministers Lianne Dalziel and David Benson-Pope for lying to or misleading the public, is not untypical, for she has adopted a different quantifying scale with Mr Peters.
The New Zealand First leader's lawyer, Brian Henry, told the privileges committee he personally paid $40,000 in court costs awarded against Mr Peters to National MP Bob Clarkson.
Mr Peters then told the committee that he repaid his lawyer, which meant he did not have to declare the sum under Parliament's rules.
However, in evidence to the committee, the Serious Fraud Office said its investigations showed Mr Peters did not repay the money; the Spencer Trust, through which NZ First's donations were channelled, did so.
Miss Clark's response to this, when questioned by journalists, was that she did not intend to waste any more time on the matter.
That may be the safest political course in an election campaign, but Miss Clark also criticised the privileges committee hearing and described it as "tainted" before it had made its final report, a shameful attempt to influence one of our legal institutions.
She was not alone. Mr Peters himself, Dr Cullen and several other members of the committee, which represents a cross-section of parties in the House, felt moved to comment on the procedures, the evidence, and the accused, and their own conclusions during the hearings which, had the matter been heard in the High Court, would surely have invited a citation for contempt.
Indeed, contempt is a word many voters might well be employing to describe the poisonous state of affairs where the MPs' behaviour and standards have sunk so low as to bring the very concept of the "people's representatives" into serious disrepair.
"Our mission," declared Helen Clark when opening her successful 1999 election campaign, "is to clean up government, and to clean up Parliament . . . the public's faith in the democratic process must be restored."
That is a pledge which voters should now measure, nine years later, and judge it to have been a spectacular failure.
