British politics are more fun today, at least for the political scientist, than at any time since the Second World War. The British two-party system, that seemingly immutable product of the “first past the post” electoral system, Britain's social structure and the enduring party identifications of Britain's voters, shows every sign of breaking up–not slowly and gradually, but with something approaching Mount St. Helen's force. A political party that did not exist a year ago, the Social Democrats, is now, in alliance with the liberals, sweeping all before it electorally. This short article tries to give some account of what is going on–and why.

The present upheaval is taking place both down below, among voters, and up above, among members of Parliament and other prominent politicians. Let us begin with the voters.