Trade, labour and politics

THERE are a lot of things about the 2016 US presidential election that nobody saw coming, and one of them is that international trade policy is likely to be a major issue in the poll campaign. What's more, the positions of the parties will be the reverse of what you might have expected: Republicans, who claim to stand for free markets, are likely to nominate a crude protectionist, leaving Democrats, with their scepticism about untrammelled markets, as the de facto defenders of relatively open trade.

But this isn't as peculiar a development as it seems. Rhetorical claims aside, Republicans have long tended in practice to be more protectionist than Democrats. And there's a reason for that difference. It's true …