Two months ago most analysts discounted the bulk of the anti-trade rhetoric coming from the Democratic presidential race as easy to wriggle out of. But as the race has got tighter and the economy has become an even greater concern to voters, Barack Obama and Hillary Clinton have become steadily more specific in their pledges.

Both candidates – and Mrs Clinton more than Mr Obama in recent weeks – have moved further to the left on the economy, in part to cater to the growing sense of vulnerability among the important blue-collar segment of the Democratic electorate.