Not for the first time, Nicky Hager has tossed a big stick of dynamite with a short, fast-burning fuse into the midst of an election campaign.
As was the case with Hager's revelations surrounding genetic engineering, which came close to derailing Labour's 2002 election campaign, the contents of his latest book, Dirty Politics, are - to say the very least - explosive.
Hager's book goes to the heart of the Government - the Prime Minister's office on the ninth floor of the Beehive - and finds something very rotten in the State of Key.
Hager's allegations are many and varied. They are extremely serious. But one stands out. The allegation that one of John Key's minions hacked into the Labour Party's database is - to put it bluntly - the modern-day equivalent of the 1972 burglary of the Democratic Party's national committee headquarters in the Watergate complex in Washington.
And everyone knows whose head rolled at the end of that saga.
If John Key wishes to avoid being labelled the Richard Nixon of New Zealand politics, he is going to have to do more than deny knowledge of what was going on in a neighbouring office. The same applies to any attempt to denigrate Hager - as Key did on Tuesday - by describing him as a "screaming left-wing conspiracy theorist". The left-wing bit is correct. But no one has ever produced the evidence to question the veracity of the content of Hager's books.
In short, Hager is credible. It is thus Key's credibility against Hager's.
The outcome of that showdown may not turn the election.
The book, however, potentially has huge ramifications for National's campaign and how the party portrays its figurehead. If Key did not know of the alleged dirty tricks being concocted in close proximity to him, then that raises questions about how loose and lax are the management, discipline and ethics under which the Prime Minister's office functions.
If the Prime Minister did know and did nothing about it, then he is skating on very thin ice.
Debate on this article is now closed.