Suddenly everything is fluid - and David Cameron is the catalyst, not Charles Kennedy's drinking. On the latter subject, any senior Liberal who claims to have been unaware of the problem before the last election is either naïve, or dishonest, or both. Poor Charlie's MPs did not move against him because of alcohol. If David Davis had been the Tory leader, Charles Kennedy would still be the Liberal leader. First blood to Mr Cameron.
The Liberal Democrats now have a choice. If they were sensible they would choose Sir Menzies Campbell, much the most impressive figure in their party. But many Lib Dem activists have spent their entire careers trying hard not to be sensible. Ming Campbell wears a Barbour; they wear an anorak, usually between their ears. If they have their way, Simon Hughes will lead them, back to obscurity.
But there are more important issues at stake than an insurrection of Lib Dem mugwumps. This is not the end of the fluidity. For years, it has been apparent that the British political system is resting on increasingly slender foundations of popular consent. Our electoral system enforces party unity. As the Lib Dems would be the first to complain, it imposes a very high entry barrier on third parties, let alone new parties. But this does not necessarily mean that the existing parties are offering the electorate what it would really want.
From the early 1980s onwards, there was an unmet public demand for the party of the centre, which would offer Thatcherism moderated by humanity. If, say, David Owen, John Smith and Michael Heseltine had been willing to establish such a party, it could have created sufficient momentum to defeat Margaret Thatcher in 1987. But John Smith was too tribally Labour and David Owen too Eurosceptic, while David Owen and Michael Heseltine were both incapable of collegiate leadership.
In 1997, Tony Blair created a party of the centre, by seizing control of a Labour party so demoralised by defeat as to be incapable of further resistance. Labour was ready for the Blairite coup and the divided Tory party was in no condition to resist. Mr Blair knew what the British people wanted: a strong free-market economy with social safety nets and excellent public services. Although he had not thought it through, he also knew that this required reform. He had no emotional attachment to stateist solutions and was sceptical about delivering change merely by spending more money.
There was only one problem. In Tony Blair's case, not thinking things through is the same as alcohol for Charles Kennedy: an addiction. Indeed, Mr Kennedy has made more determined efforts to overcome his weakness than the PM has. In Mr Blair's case, it is now too late to recover.
Nor is his coup necessarily permanent. The Labour party has always been divided between pragmatists and socialists. Mr Blair has neither eradicated the divide nor the socialists. In politics, power is centripetal, while opposition is centrifugal. As soon as Labour is back in opposition, the old splits will re-emerge.
Apropos of coups, a number of bewildered Tories now feel that they too have been subjected to one. They fear that David Cameron is also in the business of creating a centrist party. It is certainly true that in his first five weeks, Mr Cameron has been far more ruthless in challenging his party than Mr Blair was in his opening months.
Not all Tories are enjoying the process and there is a fundamental difficulty: the language has not yet caught up yet with the new reality, which is giving many Tories a problem in interpreting events.
A surprising number of Tories are still obsessed with the left-right divide within their own party. If their new leader is not willing to pay obeisance to the idols of the tribe, such as Thatcherism, might they have made a terrible mistake and saddled themselves with a leftie? Before worrying about left and right, Tories should remember where and when those terms entered general use. It was during the French Revolution, in the National Assembly. So why should any sane Tory try to divide his party along revolutionary French lines?
The Tory catechism is a simple one. Any Tory ought to love his country, its history and traditions. He should feel a tingle when he hears the National Anthem or watches the Household Cavalry riding down the Mall. A Tory believes in the state. We cannot subsist on anarchy plus the constable. Where it is needed, the state should be strong: monetary policy, the fiscal balance, defence, law and order, social welfare without dependency, standards of health and education - while using independent agencies to monitor those, just as an independent Bank of England controls interest rates.
Where it is not needed, the state should be absent. This is the opposite of the new Labour state, which is weak where it ought to be strong and interfering where it has no business to do so.
A Tory should be intellectually acrobatic enough to reconcile two contradictory beliefs: in original sin and in individual freedom. He should remind everyone that most of the greatness of British history was the work of individuals, not of governments. It follows from this that whenever possible, money should be left to fructify in the pockets of the people. Tories believe in prudent tax cuts.
Just as they fought Jacobinism then Bonapartism and subsequently resisted socialism, Tories also oppose European federalism; the latest continental evil to menace these beloved islands. Anyone who more or less subscribes to the above propositions has healthy Tory instincts and prejudices. Guided by those, without worrying whether he is a left-winger or a right-winger, he should think hard about the practical problems of government.
Again, there are a few tenets to which any hard-thinking Tory should subscribe. Does anyone seriously believe that public spending should be reduced from current levels? Does anyone doubt that, as society grows richer, the demands for first-class health and education will increase, as will the demand for law and order? In all of these areas, the government has an irreducible role. Yes, it should use market mechanisms while encouraging choice and localism. Yes, it should devolve responsibility to the professionals: more power to doctors, less to spin-doctors. But it cannot stand aside from the battle for higher standards. All this is simple, unadorned Tory common sense.
There are hard issues which have not yet been thought through, including immigration and the nature of Britain's non-federal relationship with Europe. But any Tory who doubts David Cameron's commitment to Britain's welfare does not know David Cameron. Mr Cameron believes that he can change his party in order to give the public a potential government that it will vote for, while remaining true to Tory values and principles. In response, there is no need for Tories to jettison all their scepticism. But they ought at least to greet what has happened with a cautious "so far, so good".