If UK Prime Minister Boris Johnson seems rather glib about the idea of his country crashing out of the European Union without a deal – an outcome that myriad authoritative bodies have predicted will be highly costly for the UK economy -- it is most likely because there is something he fears more than that. Nigel Farage’s Brexit Party is far from a real opposition party.

It doesn’t have a single member of parliament. It may even have peaked in the polls since Johnson took the Conservative Party reins. But it could easily pose a threat to the Conservatives winning an ...