Tony Blair will have nothing but support from politicians on all sides in the Commons as he fights to overcome his recurring health problems.
BBC News Online political correspondent
And, as he has said himself, his heart flutter alone is not enough to automatically end his premiership or make him incapable of contesting the next election or continuing in Downing Street if he wins it.
What will have stunned many and infuriated a good number, however, is his insistence that he intends to out-do Margaret Thatcher and serve a full third term as prime minister if he wins.
Whether Chancellor Gordon Brown had been informed of this decision before the prime minister announced it is not known.
United front - but for how long?
But if Mr Brown or his allies were holding out hopes of a swift succession they have been sensationally dashed.
The prime minister's comment that "there are lots of people who want to do the job" certainly won't help calm them down either.
It is unprecedented in modern times for a prime minister to set out his leadership plans so precisely.
Mr Blair has said, if elected, he will serve a full third term but quit and spark a leadership election shortly before the election for a fourth term.
Winning a third term would be an historic victory for Labour and only the most wildly optimistic, apparently including Mr Blair himself, believe they could then go on to win a fourth.
So Mr Brown may now be facing the distinct possibility that he will never become prime minister. And that raises one obvious question.
Will the Brown camp believe they have nothing to lose by moving against Mr Blair now - before the next general election?
They may consider they will not get a better chance of turning on their leader while he is at a weak point. And, despite his upbeat mood, the prime minister is undoubtedly weak.
He cannot, and clearly never will throw off the shadow of Iraq which has dogged him since the war. His attempt to move on at his party conference appears to have made little difference to the level of opposition to his leadership over that decision.
So he remains politically weakened by that. There are even those now wondering if his uncharacteristically poor performance as he delivered his big speech - along with a couple of rocky performances just before his summer holiday - was a result of his health problems.
Some will also ask whether they want to be led into a tough election campaign by a leader with such health problems, no matter how successfully they have been dealt with.
Finally, health has traditionally been an "excuse" used by many of his predecessors to retire. In the political jungle, that is a dangerous combination.
The prime minister is well aware of all this and those considerations have almost certainly led to his extraordinary announcement.
His decision to set out a clear end to his reign may be an attempt to shut down all the leadership chatter now while offering his would-be successors a clear target to look forward to.
It was also an attempt to shut down the planned Tory election slogan "vote Blair get Brown."
Still, the prime minister's claim that his statement might be a little unusual was one of the understatements of the century.
Whether it succeeds to end the speculation over his future or actually intensify it remains to be seen.