Mr Blair may end up as a PM without a party

It is a mistake to suppose that war consolidates a Prime Minister's position. It is equally – perhaps more – likely to make it less stable or to bring it to an end completely. HH Asquith fell because he was not prosecuting the First World War vigorously enough. His successor, David Lloyd George, fell largely because he was vicariously fighting another war, between the Greeks and the Turks, with altogether too much vigour. The Conservatives on whom he depended supported Turkey; whereas Lloyd George supported Greece, which he fancifully thought was the same as Wales. Neville Chamberlain fell because of military failure; Anthony Eden for the same reason, and also because he had gone off his head.

Margaret Thatcher's last action in the Cabinet was to inform her colleagues of the dispatch of reinforcements to the troops already in the Gulf. But her fall was not brought about by our participation in this earlier – and legally very different – war. She was not blamed for it. Indeed, no one mentioned it. Certainly in all the comings and goings, no one objected: "We can't get rid of the PM when we're just about to go to war." The matter was simply not raised.

There is another historical precedent which Mr Tony Blair may like to ponder. It has nothing to do with war; or not directly. It is the case of Ramsay MacDonald and the formation of the supposedly National government in 1931.

MacDonald has not been treated well by history. In his day, politics was less led by personalities. Even so, to the electors MacDonald was the Labour Party. He was among the most gifted orators of the last century, in the same class as Aneurin Bevan or Lloyd George, though he was to lapse later into incoherence. For over 10 years he and the Conservative Stanley Baldwin dominated politics as Mr Blair has since the mid-1990s – or as the almost equally forgotten Harold Wilson once did.

But if history has been unkind to MacDonald, the party itself has been positively brutal. His picture has been turned permanently to the wall. He is the traitor, the Prime Minister who deserted his party to inaugurate what were in reality 14 years of Conservative rule, ending only with the great victory of 1945. This other picture is so fixed that it is doubtful whether any amount of evidence will now displace it. And yet MacDonald was an honourable man, not only by his own but by any standards. Though personally vain, he was not attached to power for its own sake.

The background was an international financial crisis with a run on the pound, which several post-1945 Chancellors experienced but which Mr Gordon Brown has yet to undergo. The Bank of England and various US banks demanded a cut in unemployment benefit. The Labour Cabinet agreed to the cuts demanded by a majority of 11 to nine and then promptly decided to resign. MacDonald agreed to resign with them. Over one long weekend, he tried to resign three times. Each time George V refused to accept his offer. He told MacDonald it was his duty to form a National government. Eventually he gave in to the King. He took only three cabinet colleagues with him into the new government, which had the support of eight Labour MPs. It was confirmed in office with a thumping majority at the subsequent general election.

For the next four years (he was replaced by Baldwin in 1935), MacDonald found himself a Prime Minister without a party. So had Lloyd George been in 1922, dependent as he was on Conservative votes which were then withdrawn. Mr Blair may now be going the same way. He too may be turning himself into a Prime Minister without a party.

So far, Mr Blair has enjoyed the most extraordinary good fortune in his forays overseas. The business in Sierra Leone was the kind of neo-colonialist African adventure in which the French have long specialised. The wars in Kosovo and Afghanistan turned out all right both for Mr Blair and for successive US Presidents, though many people were killed in the process. But, fortunately, they were the right people. It is a convenient new doctrine that, in any properly conducted war, only those on one side are ever actually killed. And it must all be over quickly. As Lord Copper puts it in Scoop:

"They must win quickly. The British public has no interest in a war which drags on indecisively. A few sharp victories, some conspicuous acts of bravery ... and a colourful entry into the capital. That is The Beast Policy for the war."

It is likewise the policy of Mr Blair, the Bank of England and the City for any war in Iraq. But his troubles will start well before we have the opportunity of judging whether the war is going to be long or short. I have no doubt Mr Blair believes that a second UN resolution is desirable before any military action is taken. But he does not believe it to be morally or legally necessary. Both and he and Mr Jack Straw have said over and over again that, on receipt of an unfavourable inspectors' report, action can be taken without any further formalities.

Indeed, at Prime Minister's Questions Mr Blair seemed to be saying that military action was justified in any event, because it was morally superior to the maintenance of sanctions, whose malign consequences for the Iraqi people had been brought about by Saddam Hussein's perverse interpretation of them. That sanctions have caused misery is not our fault but Saddam's. Accordingly we are justified in attacking his people to avoid any further suffering on their part. Such is Mr Blair's logic.

But he knows now, if he did not know at the beginning, that a second resolution is necessary – though it may still not be sufficient – if he is to carry his party with him. At the beginning he said that he would not allow an "unreasonable" veto from one of the permanent members of the Security Council to deflect him and Mr George Bush from their chosen course. Then (it was a few weeks ago) it did not seem likely that China, France or Russia would produce the black ball: they would be content merely to abstain. It also seemed probable that the nine votes required from all the members of the council could be acquired without any real difficulty.

Today neither the absence of a veto nor the acquisition of a majority looks nearly so free of trouble. At the same time opinion in the parliamentary party and in the country alike has hardened. It does not see why Mr Blair and Mr Bush should be allowed to make up the rules of the UN as they go along or to get away with saying that the whole world is out of step except our Tony and our George. And Mr Blair may soon find himself relying on Tory votes, just as MacDonald did.