DISRUPTION seems to be the rule in politics as well as in business. Economic churn is promoting discontent with the status quo while technological innovation is making life easier for upstarts. The result is that long-established political parties such as France’s Socialists and Greece’s Pasok have crumbled, while insurgents have come from nowhere to form governments (in the case of Greece’s Syriza) or shake things up (like Italy’s Five Star Movement). Neither of France’s main parties has a candidate in the final round of the election on May 7th. In America Donald Trump has mounted a hostile takeover of the Republican Party. Yet in Britain the world’s oldest political party is marching to an easy victory in the general election. The country has endured a decade of stagnation and austerity. Its public services are strained to breaking point. The Brexit referendum delivered the biggest shock to the political establishment since Suez and divided Britain down the middle. Yet the only question that troubles psephologists is whether the Tories will get a “small” majority of 30 or so or a blowout of more than 100. Since Benjamin Disraeli pronounced that his...