On 1 October 2004, as he was leaving that year’s Labour Party conference, the then Prime Minister Tony Blair gave an interview to the BBC’s Andrew Marr which sent shockwaves through the political world.
Ostensibly, the point of the interview was to reassure the public of his fitness to govern ahead of a routine operation to correct a heart flutter that he was due to undergo the following day.
But things were never quite as they seemed with Mr Blair, and the real point of the set-piece encounter was to announce his intention to continue as Prime Minister for a further five years.
“If I am elected, I would serve a full third term. I do not want to serve a fourth term - I don’t think the British people would want a prime minister to go on that long. But I think it’s sensible to make plain my intention now,” he said.
At the time, it was seen as a dramatic reassertion of Mr Blair’s authority after a period marked by open speculation about whether he would even see out his second term, let alone fight for a third.
Significantly, the interview took place when Gordon Brown, his putative successor, was out of the country, leading one key Brown ally to liken Mr Blair’s actions to an “African coup.”
Yet of course history shows that, in the longer-run, the disclosure that he would not fight a fourth election as leader served not to enhance Mr Blair’s authority, but to fatally undermine it.
Far from serving a “full third term” as Prime Minister, Mr Blair managed only two-and-a-bit years of it before finally being forced to give way to Mr Brown in the summer of 2007.
So why did David Cameron risk making exactly the same mistake this week by setting a leave-by date on his own premiership?
Just like Mr Blair a decade ago, the Prime Minister revealed that the forthcoming election would be his last, and once again it was a BBC journalist, this time James Landale, who was the recipient of the scoop.
Mr Cameron actually went further, not only putting a time-limit on his spell in Number 10 but actually naming three potential successors in George Osborne, Theresa May and Boris Johnson.
A straight answer to a straight question, as the Tory spinners would have it? Or a monumental gaffe that will fire the starting gun on a leadership battle that, for Mr Cameron, can only end in tears?
Time will tell. But in the short-term, the political impact of the Prime Minister’s comments may be limited.
While it may cause some voters to believe he is taking the May 7 election contest somewhat for granted, his comments appear to have shifted the focus away from the question of whether he will win and towards the question of how long he will stay – which could be no bad thing.
The longer-term consequences, though, are likely to be less palatable for Mr Cameron, as the central narrative of his government becomes ‘When is he going to go?’ and ‘Who will take over?’
Even if he does go on and win a second term, he may find his power inexorably starting to drain away as ministers and MPs become more concerned about currying favour with the next leader than the present one.
That’s still a very big if, of course. The opinion polls still have the two main parties more or less neck and neck and the smart money remains very much on another hung Parliament.
And should Mr Cameron fail, for the second election running, to win an outright majority against an opponent whom few Tories rate, that leadership race that he spoke about this week will get under way a lot sooner than he thinks.
Thursday’s ‘Battle for Number 10’ programme – a very poor substitute for the head-to-head debate the broadcasters and the public wanted – was so dull it seems unlikely to shift any floating voters.
Only a gaffe of ‘Duffygate’-style proportions now seems likely to break the deadlock.
There was talk this week of a “Save Dave” campaign being launched in the event of an inconclusive result, with Tory MPs urged to take to the airwaves on May 8 to shore up Mr Cameron’s leadership.
But the days when the likes of Harold Wilson or Ted Heath could lose an election and then live to fight another day have long since passed.
The clash between Messrs Cameron and Miliband is not just a ‘battle for Number 10’ but also an existential battle for political survival.
By the second week of May one of them will be Britain’s Prime Minister. The other will be toast.