Analysis By Nick Assinder BBC News Online political correspondent

It may be an uncharitable thought - but, for many, the latest row over Tony Blair's future has all the hallmarks of a botched spin operation.

Blair's leadership is matter of speculation

It is suggested that, in an attempt to kill off the runaway speculation over his leadership, someone senior was encouraged to place newspaper stories that the prime minister had no intention of quitting either now, or after the next election.

It may only have been a re-statement of the official line, that, voters willing, Mr Blair planned to fight and win the next election and then serve a full term.

But in politics, timing is everything. And with speculation in Westminster reaching a new level, this was undoubtedly a good time to try and stop the chatter.

If that was the aim, and it must remain an if, then it has comprehensively backfired and served only to fan the flames.

Lame duck

In the often-surreal world of Westminster politics, an on the record re-statement of the official line would have provoked little comment.

That would have been seen as the only sensible, safe response the prime minister, or anyone speaking on his behalf, could give.

Thatcher pledged to go on and on

You cannot, after all, have a prime minister announcing his retirement plans in advance - thus becoming a lame duck - or declaring that he plans to win an election only to hand over to someone else afterwards- that looks undemocratic.

But a private briefing of precisely the same statement looks like something different. It begins to look like a genuine statement of intent - that Tony Blair really does plan to go "on and on".

That exact declaration did Margaret Thatcher no good whatsoever when she made it a year before being ousted by her party.

And Mr Blair would be risking Gordon Brown's wrath by appearing determined to stymie his prime ministerial ambitions.

The family

So, unsurprisingly, Downing Street angrily denied there was any such conspiracy and re-stated the official line.

But it looks like this outbreak of leadership speculation has some way to run yet.

No prime minister can go on for ever. The trick is to spot the point at which you are at your peak, and go before the inevitable rot sets in and certainly before your party dumps you.

And, for Tony Blair, the family will also play a central role in his decision.

It is a difficult calculation, that is why prime ministers virtually never get it right and the old adage that all political careers end in failure is so accurate.

Seven years into the job, there is bound to be gossip about the prime minister's intentions and that has not been helped by a terrible few months for him over Iraq, immigration and Europe.

And it is absolutely the case that more Labour MPs than ever before are ready to believe that Mr Blair could go at almost any time.

Whether anyone has a genuine insight into the prime minister's thinking is an entirely different matter.