Comment Central: What does it all really mean?

John F. Kennedy, always the cooler, more considered, of the Kennedys, watched his brother Robert dive off a sailboat into frigid waters off the coast of Maine, laughed and shook his head. He remarked to his close aide Ted Sorensen: “Well, that either showed a lot of guts, or no sense at all, depending how you look at it.”

Sorensen recalled these words when he found himself riding in Robert Kennedy's campaign plane, supporting a presidential bid that most of the old JFK team, including him, believed was doomed. Bobby Kennedy's 1968 campaign, taking on a sitting president in his own party, either showed guts or no sense at all. It depended how you looked at it.

Robert Kennedy hated President Johnson. “He's mean, bitter, a vicious animal in many ways,” Kennedy complained. His young advisers thought LBJ was sure to lose in the end in 1968 whatever Bobby did. And if LBJ lost, and Kennedy stayed out of the race, then Kennedy would go down with him. It would be “eclipse - irretrievable”, his trusted aide Adam Walinsky warned him. Yet still, Kennedy had hesitated before running.

There were good political reasons for this hesitation. In his compelling book on Kennedy's 1968 effort, The Last Campaign, Thurston Clarke explains how the more seasoned “honorary Kennedys”, JFK's extended family of advisers, joined forces with the Democratic establishment to urge RFK to stay out. He couldn't win the nomination, they said. He'd just spoil it for Johnson. And in the background there was always the possibility, the nagging thought, that it could all end in tragedy. As it did. Friday marks the doleful anniversary of Bobby's assassination.

So why did Kennedy do it? Why did he take the plunge? What turned his confident public statements that he would not run into a decision to go for it? In one word - Vietnam.

Kennedy could not support Johnson through the campaign as a war that he hated continued to escalate. Political considerations could be balanced. This couldn't. He could not stay silent; he had to make the case. And when he had finally decided to take the plunge he told friends: “I don't know what is going to happen, but at least I'm at peace with myself.” Clarke believes that, in the end, Kennedy felt morally compelled to stand.

The decision Kennedy agonised over - to challenge for the crown, or not to - must surely be in the minds of some of Gordon Brown's Cabinet today. Those that are left, that is. Surely they can see what the rest of us can see. That Labour led by Mr Brown is doomed to terrible, catastrophic defeat. That no one, no one, could lead Labour to a worse defeat than he. That - as Jacqui Smith and Tom Watson showed yesterday by decamping - waiting it out for another year does not bring dignified defeat for a united government.

What could possibly be stopping them, then? Why is the departure of Gordon Brown as Labour leader still only a possibility and not a certainty?

The first reason is what one might call the Bobby Kennedy reason. Mr Brown's critics do not have a Vietnam War to compel them to act. They only have the hedged-about political considerations that led RFK to hesitate. If Cabinet ministers were to call for Mr Brown to go, what would they cite as the reason? Merely that Mr Brown would lead Labour to defeat? That may be of interest to the Labour Party, but hardly to the rest of us. It certainly doesn't constitute a moral case for action.

When Michael Heseltine stood against Margaret Thatcher, he offered a clear change of direction. So did John Redwood when he challenged John Major. Both felt that they could no longer stand aside, that they needed to make their case. They believed that their moment had come. Is there anyone in the Cabinet of whom that is true now? Upon what grounds?

If Mr Brown survives, there is something else he can thank - the fact that there is a market failure in the market for political coups.

It is tempting to use social psychology to analyse the behaviour of the Labour Cabinet. One could suggest that they are adhering to a social norm, going along with the group. Just as hundreds of followers of the Reverend Jim Jones drank poison just to fit in, so Cabinet ministers are keeping quiet as they all commit suicide together. But this description doesn't quite fit. Because, unlike Jones's followers, most individual Cabinet ministers are only too aware of what is going on. And they don't want to die.

So economics provides a better way of understanding why they still might not act. A market failure can exist where it is impossible for people to gain the full benefit of the costs that they incur by acting. And this may yet save Mr Brown.

The benefit of Brown's demise - increased support for Labour - is shared among most members of the Labour Party. The cost - the risk of sticking your head above the parapet and then finding no one else has joined you - is concentrated on the person doing the head-sticking. It could be in everyone's interest for Mr Brown to go, but still in no one person's interest to start the movement against him. Naturally someone could decide to move, heedless of this calculation. But market failure explains why such an obviously sensible thing for Labour to do might yet remain undone.

There is a final reason. Let's call it the World Cup reason. Brazil were the best team in the last football World Cup. In any game they played, they were favourites. Yet it still remained unlikely they would win the whole tournament. And they didn't. The reason is simple statistics. A string of things, each of which are probable, taken together become improbable. It was very likely that Brazil would win any one individual match, but unlikely they would win them all.

It is very probable that Labour will achieve such a bad result tomorrow that the party will be jolted. It is very probable that in the next week one or more Labour MPs may announce that it is time for Mr Brown to go. It is very probable that Mr Brown could be forced out if there were a revolt. But for all three things to happen? That's a great deal less probable.

It is hard to believe, isn't it, that Gordon Brown can carry on like this. It's extraordinary to think he might. But, really, he can. He shouldn't do, he might not, but he can.

daniel.finkelstein@thetimes.co.uk

Times Recommends

• Resist urge to throw voters red meat
• Slay sacred cows and be candid
• We cannot let these 100 deaths deflect us