For amateurs, it's an absorbing, if macabre, parlour game. For professionals in politics, diplomacy and the like, it's a routine exercise in thinking the all too thinkable. You take an individual, the more powerful the better, and consider the implications if he, or she, were felled by an assassin's bullet – or, as a softer British version might have it, run over by a No 24 bus.
The trouble with such exercises is that the fatal strike invariably comes out of the blue and the consequences rarely run according to any script: John Smith's heart attack that opened the Labour leadership to Tony Blair; the death of Princess Diana that shook the British monarchy; the murder of Itzhak Rabin which froze the Middle East peace process; the killing of Rafiq Hariri, which precipitated Lebanon's "cedar revolution". And, of course, the assassinations of John F Kennedy and Martin Luther King, which cast their shadow over the United States to this day.
Had we dabbled in this sort of contingency planning in recent weeks, the "favourites" might well have included George Bush, Pervez Musharraf or Robert Mugabe. Yesterday, though, a new and, at first sight, improbable candidate emerged. According to the Russian Interfax news agency, suicide bombers had plotted to kill Vladimir Putin during his visit to Iran.
Quite why President Putin was to be targeted in Iran – presumably, though this is not spelt out, by Iranian assassins – is not easy to divine. The most plausible explanation might be an attempt by Islamic militants to avenge Putin's prosecution of the Chechen war. Or perhaps a section of extreme Iranian opinion believes Putin is deliberately stalling on nuclear co-operation in order to please the Americans. That said, Putin – whose security is nothing like the armoured cocoon of a US President or even a British Prime Minister – would be at least as vulnerable in his own country as visiting Iran.
Whether or not you find the Interfax report credible – and there must be questions about it – it is not hard to imagine the frisson, not least in certain Russian émigré circles, at the prospect of Russia suddenly without Vladimir Putin. Nor is it only his exiled enemies who might think that a well-primed bomb in Tehran would simplify their lives. There is a broad swathe of Western opinion that regards Putin as a malign force in Russia and abroad. They would not go so far as to engineer his departure from this life but, if it were somehow to happen, they would not shed many tears. They would instead hail the bright new future, assuming that without Putin, Russia would be a mere hop, skip and jump away from embracing no-holds-barred democracy, signing up to "universal values" and beaming beatifically on the world.
Such thoughts might be agreeable, but they are utterly delusional. Putin has an approval rating in Russia of 70-80 per cent. He is widely credited with bringing the stability and relative prosperity of recent years. Already, his planned departure from the presidency next March is causing domestic ructions. From the cabinet to the KGB, Putin associates are jockeying apprehensively for their futures. The sense of uncertainty, panic even, if Putin were suddenly out of the equation, can well be imagined. Russia would be fortunate to escape an open power struggle – with predictably adverse consequences for the wellbeing of the country and its people.
Whoever took power, or emerged from that tussle, would show a harsh face to Russians and to the outside world, regardless of personal inclination. Think of the United States after the destruction of the World Trade Centre, and apply that to Russia. All the old paranoia would return. Civil liberties, even in their current imperfect state, would be thrown from the window, and many a Russian would cheer them as they fell. Torn between curling up and lashing out, Russia would not be the compliant neighbour and partner Putin's foreign critics hanker for; it would be nervous and unpredictable for years to come. Any thought that a Russia that had just lost its President to terrorism would immediately make common cause with the US against militant Islam can be discounted. And if it did, would this be such a good idea?
Putin has his faults. He is quick to anger and harbours grudges. His understanding of Western democracy seems imperfect; his concern for Russia's dignity can make him difficult to deal with. But he leads a country that is richer, stronger, and far more at ease with itself than it was when he took office eight years ago. All those tempted to believe, even fleetingly, that a Russia without Putin would be either safer or better, must be more careful about what they wish for.