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.. Why have I quit the Conservative Party - and joined the Liberal Democrats? Let me dismiss out of hand some of the implausible explanations generated by the Conservative Central Office propaganda machine in the past 48 hours. I can assure readers of the Independent that it has not been out of "ambitious careerism" or "personal pique". These attempts at trivialisation of what has been an agonisingly difficult personal decision are unworthy, although perhaps not surprising. But they also underestimate the nature of the crisis that besets the Government of this country and our whole political system, which have led me to this decision.The Conservative government led by John Major seems paralysed by indecision, waiting for an election which cannot long be delayed and relying increasingly on the worst, hard-faced, populist instincts of people who would have been no more than a small and disregarded right-wing pressure group in the Tory party that I joined 21 years ago. The party has changed - and for the worse.Nowhere, however, is the absence of strong strategic leadership more serious than on the issue of our membership of the European Union. We are now witnessing as serious a chasm in the governing party on this issue as the Conservatives experienced on the issue of the Corn Laws in the 19th century.Unfortunately, and this has been decisive for me, it seems that the Prime Minister has come down on the side of chauvinism, reflected not only in growing Euro-scepticism from the Cabinet but in profoundly illiberal attitudes towards ethnic minorities and such unfortunate people as asylum- seekers.Europe is our present and our future.

That is why I have been dismayed that the lack of decisive leadership has threatened the advance we need to make to reach the heart of Europe. That is where Britain must be to exert its full influence, both for its own benefit and for all the nation states of the European Union, and to work together for "la culture de la paix", with international solutions to problems and conflicts worldwide.For instance, I am involved in a campaign to promote understanding between the European and Islamic civilisations, so important on Europe's eastern borders, as we have seen in Bosnia and in our relations with Turkey.We must draw upon the European Union's great strengths while correcting its weaknesses in order to derive the maximum benefit. We certainly need more openness, democracy and tolerance in Europe, but getting Europe right is the most important issue for our nation and every one of our citizens - for their prosperity, their jobs, their welfare and their well-being.It is no good procrastinating, abandoning or fudging great principles and hopes in order to satisfy the Little Englanders The debate was long ago joined and the issue decided. We have already had one referendum confirming our membership.We should heed Ted Heath's warnings made yesterday in response to my concerns: "There is no future for Britain outside Europe. The rest of the world realises that and is astonished that we should even risk it.

As therefore our future is in it, let us be positive about it and make a success out of it for ourselves and our fellow members." My own sentiments exactly. I am a Euro-pragmatist who wants to work inside the Community instead of standing sneering on the touchlines.If Europe has been the catalyst for my decision, there have been a host of other causes which have come together in such a way that unease has turned to disenchantment and, in the end, to this tough parting of the ways.One example is education I have a great personal commitment to better education. I want every child to have the opportunity, as of right, to develop his or her potential and talents. Not just the sons and daughters of the rich and the middle classes, but also those in our most deprived villages, city areas and housing estates They deserve that right as well. I want smaller classes, better teachers, a generous supply of textbooks and other literature, computer technology and modern buildings to replace those that are old and dilapidated That means investment. But it is essential that we invest in our children, who are our nation's future, both morally and intellectually.On the crucial issues that matter most to me - such as Europe - the Liberal Democrats have been clear and consistent. On education they have made a pledge to raise standards, even if it means higher personal taxation.