R ightwing populists always promise they will get things done when they get into power. Immigration will be halted. Government waste will be eradicated. Traditional values will be revived. National decline will be halted. National greatness will be restored. Relations with the outside world will be redrawn. Great tasks that, for decades, have been beyond the capability and will of conventional, compromising politicians will be accomplished – and fast. Populist governments will respond decisively to voters’ accumulated frustrations, cut through bureaucracy, and avoid the delays, U-turns and half-finished projects that usually blight democracies. The business of government will be straightforward and highly productive – even heroic – rather than complicated and disappointing. From Donald Trump’s ultra-confident social-media posts to Nigel Farage’s sweeping pledges at press conferences, rightwing populism is never knowingly undersold.…