Is it just Emma - or is it really The End?

Disaster or comedy? The creak that leads to the crash of the Tory administration, or the squeak of a disappointed and lonely backbencher? Emma Nicholson's defection brought down almost biblical wrath from the party hierarchy; they have accused her of inconsistency, caprice, wounded vanity. She accused them of racism and general beastliness.

Well, she has been inconsistent (but so are most of the Cabinet). And she is composed of personal ambition and vanity, alongside public-spiritedness and idealism (they, too.) Both fleeing woman and fled-from party abominate the other as extraordinary, untrustworthy and bizarre. Sensible observers will no doubt be mildly amused by the raised and raucous voices breaking through the new year atmosphere and wonder only whether it means an early election. Is it just Emma or is it The End?

The Government's majority, on paper, is now five. I include the whipless Sir Richard Body, who has promised to back John Major in any confidence motion - rather decently, one thinks, since he is openly regarded by the Prime Minister as a loony.

Assuming the Government loses its two by-elections, that falls to three - the same as Harold Wilson in 1965-66 and three more than James Callaghan inherited in 1976. Given that both stayed in office, with Wilson completing 64 government Bills in his first parliamentary session before going on to win the 1966 election and Callaghan stomping on for nearly three years with the help of the Lib-Lab pact, that might not seem so bad.

This time, though, the Government seems wrinkled and tired, not young like Labour in the mid-Sixties. And it has no Liberal support waiting in the wings, only the Ulster Unionists. They are unenthusiastic about Major, yet seem unwilling to strike him down. This kind of support is fraught with danger. The Unionists have left open the possibility of a sudden change of mind, which could happen on almost any issue at almost any time. David Trimble and Mo Mowlam, Labour's Northern Ireland frontbencher, become even more important players than before. The greatest political danger is to the peace process itself, since Major's parliamentary weakness will further inflame nationalist suspicions. But the Unionist bloc now becomes vital to the politics of the year ahead.

Courtesy of Trimble, the Conservatives could still go the whole way to spring 1997. Throughout the Maastricht rebellion, Major's real majority was, on a series of important issues, even lower than it is this morning.

To state that, though, is only to begin the reckoning. For the hidden cause of the two centre-left defections from the Tory party in recent months derives from the Prime Minister's handling of the rebellion then. The rebels behaved with such nerve and discipline that Major decided he had to focus all his attention on the right - placating, haranguing, charming and eventually confronting them, while taking the Tory left for granted.

He calculated that the Conservatives were moving remorselessly rightwards; his own speeches at times reflected this drift (it has never been a lurch), and his own position on European integration hardened. Pro-European ministers and backbenchers fumed and spoke privately of their despair. But for a time nothing happened.

What Major may have forgotten is that while the Tory right was virtually obliged to maximise its influence by forming cabals within the party (for they have nowhere else to go), the Tory left was starting to see an alternative politics opening up. In a parallel way, after the Callaghan years the Labour left plotted and caballed inside the party (for they had nowhere else to go) while the Labour centre-right broke away to form the SDP.

In recent years we have become used to the allure of the moderate, pro- European, reformist agenda of Tony Blair and Paddy Ashdown for former Tory voters and activists. But Tory politicians have eyes to see and ears to hear, just like their followers. Neither Nicholson nor Alan Howarth were typical Conservative MPs. Their social consciences were worryingly overdeveloped, unfashionably serious and occasionally a mild embarrassment. But if the Conservative Party really does move to a mix of anti-Europeanism and Newt Gingrich-style radicalism - "a Little England and Smaller State" - then such people may be outriders for a bigger shift.

Am I predicting a Christian Democrat breakaway to mimic the SDP? No, history never quite repeats itself. The SDP happened to a shattered party in opposition, whose ideologues were trying to drag it against the flow of world history. The numbers involved and the seniority of the defectors were of a quite different order to now. The Roy Jenkinses, Shirley Williamses and David Owens of moderate Toryism - Leon Brittan, Lord Howe, Chris Patten, Kenneth Clarke - are still loyal. But there is life in the comparison, all the same.

Consider: how did the SDP most hurt Labour? It was less by hard electoral challenge, more the deadly message sent to the whole British electorate that Labour was extreme, no longer a party for "the rest of us". Voters were already inclined to believe this, and Labour took well over a decade to recover.

The Conservatives are still in office, and in their case it might only take a few defectors making a similar point about extremism and a few more speeches from Michael Portillo of the kind he gave at last year's party conference for the image of Tory wildness to take hold in people's minds. If so, the disorganised flight by a handful of backbench MPs could have almost as harmful an impact on the Conservatives as the whole complex saga of the SDP had on Labour.

And there will be some more reckoning yet. The experience of Wilson in 1964-66 and then in 1974-76, and of Callaghan in 1976-79, was that although governing on a small or nil majority was possible and brought modest daily triumphs, it was destructive in the longer term. They were in office and even in power - but rarely in authority. Their reputations were dulled by the twisting, wheedling and deal-making to keep their governments alive; the 'fudge and mudge" from which Owen famously revolted was a habit of mind tutored by years of close late-night votes in the Commons.

There is a logic at work here. Small majorities make leaders compromise with the wild men of their party; such compromises repel the moderate supporters and in time the whole party is tainted as wild. It has happened before. It is happening now. It may not have an impact on the timing of the election; but it will surely have an impact on the result, which matters rather more.

The damage done by posturing tribunes on the Tory right to their party's prospects is incalculable. However great the fury of Tory leaders about Nicholson's defection, they should remember that the public cares far less than they for that obscure quality, party loyalty; it is far more interested in her message about extremism, and is listening attentively to the tone and timbre of their accusing voices. Be calm, gentlemen; be calm and be a little humble - you have no better option left.