The splits in the Conservative Party over Europe are deep and probably unbridgeable. The recent departure of two Conservative MEPs - though, in my view, premature - is nevertheless deeply significant.
But though Europe is the flashpoint, the divisions in the Conservative Party now reach far beyond this single issue. More than at any other point this century, the Conservative Party is now two parties - two parties at war with one another - who are held together not by common beliefs, but only by electoral expediency.
It is a loveless marriage, held together by the strait-jacket of First Past the Post. But slowly, as the strait-jacket is loosened, the marriage is unravelling.
The potential of Proportional Representation [PR] to jemmy open cracks in our party monoliths is not limited to the Conservative Party. The Labour Party, too, though it hides it better, is irrevocably split. Not over Europe, this time, but over socialism. One part of the Labour Party believes in it. One part does not. And in the middle, a few tortured souls run around desperately trying to redefine it to cover the latest development.
There are today not three, but five political parties in British politics. Two Conservative Parties. And two Labour Parties too. And Old Labour are just as far from influence and power as the Conservatives.
In the Labour Party, too, there are hints of what may be to come. The effective deselection of Old Labour MEPs, for which New Labour has opportunistically used this year's change in voting system as an excuse, but which would probably have happened anyway. The refusal to approve Dennis Canavan for the Scottish elections, for little more than being an old-style socialist. The setting up of Arthur Scargill's Socialist Labour Party.
Under our current system a breakaway of the left is not impossible, and they could well be pushed into it, for Tony Blair would not miss them. But it could come about only from total desperation, for it would be doomed from the start.
Yet under PR there would be hope. In some parts of the country, 10 per cent of the vote would not be beyond their reach and a new party of socialists, credibly led, could reasonably hope to win a small group in Parliament, although I wouldn't personally recommend it to voters. That would be the honest way for the two sides of the Labour Party to resolve their differences. No more internal appeasement, no more loveless marriages.
Now, having touched on Labour and the Tories, I'd better say a word about the Lib Dems. There is a misconception among some commentators - and perhaps even some high in the Labour Party - about the long-term aims of our co-operation with Labour. They misunderstand what the "political realignment" is that we are seeking. They assume that the aim is to create one single, huge, hegemonic party of the centre left, reducing choice for electors. Let me state clearly, this is not my vision and it never has been.
In fact, my aim is quite the opposite. I am not in the business of predicting the overall state of British politics in 10 or 15 years' time. But my aim is to help create a political environment where people can work together without having to be in the same party. And where voters at election time can choose not just between two uncomfortable coalitions, but between each major strand of current political thought.
Can it really be right that when a voter goes to the polls they can make no distinction between whether they are supporting the Labour Party of Tony Blair or the Labour Party of Tony Benn? Or whether they are voting for the Conservative Party of Michael Howard or that of Michael Heseltine?
Maybe, in a time before mass media, people's ability to choose between their politicians was limited to a simple choice of A or B. But surely now we have gone beyond that?
Proportional Representation is the means by which parties, large and small, can have sensible and constructive relationships with other parties without being destroyed in the process. It would create a new dynamic, enabling small, independent parties to thrive, rather than drawing them into catch-all coalitions. Pluralism and diversity would be entrenched into our politics.