“Populism” may well have been the defining word of the previous decade: a shorthand for the insurgent parties that came to prominence in the 2010s, challenging the dominance of the liberal centre. But no sooner had it become the main rubric for discussing both the far left and far right than commentators began to question its validity: worrying that it was too vague, or too pejorative, or fuelling the forces to which it referred.