AGHAST at the defection of millions who voted for Barack Obama in 2012 but for Donald Trump in 2016—notably working-class whites in the Midwest—the left wants the Democratic Party to snatch up the banner of economic populism and declare war on Wall Street, big business and other global elites. At post-election gatherings like the Democracy Alliance conference in Washington, DC, it is an article of faith that Senator Bernie Sanders of Vermont, the snowy-haired, finger-jabbing scold who lost the Democratic presidential primary to Hillary Clinton, would have trounced Mr Trump in the general election.

Such Democrats are making a mistake. It is as if America’s political classes are bent on copying every part of Britain’s current flirtation with who-needs-experts populism. Not content with holding an election that saw voters sharply divided by education, age, geography and attitudes to social change—as happened with the Brexit referendum—American leftists seem ready to follow Britain’s Labour Party down the path of self-righteous irrelevance. On November 14th protesters were arrested after a sit-in in the office of the Democratic leader in the Senate, Charles Schumer of New York, blaming him and other “Wall Street Democrats” for Mr Trump’s victory and demanding that he step aside in favour of Mr Sanders or another leftist icon, Senator Elizabeth Warren of Massachusetts.

Sanders-boosters point to polls, taken months ago, that showed him beating Mr Trump in a head-to-head contest. His “the system is rigged” rhetoric made him the Republican’s equal when it came to indignation, supporters note, while his rumpled asceticism (he is one of the poorest members of the Senate) and plain-spoken integrity made him a more convincing anti-establishment champion than Mrs Clinton. Because the election was so close, decided in just a few battleground states, Mr Sanders could have won by convincing a few hundred thousand workers angry about globalisation and free trade.

The Democratic left is missing a crucial detail: those surveys were taken when most Americans knew little about Mr Sanders. When Lexington conducted an unscientific straw poll of prominent Democrats in Washington this week, they were strikingly cautious about declaring the Vermont senator a national champion. For every Trump vote that Bernie Sanders would have won, his positions could have cost Democrats support from other voter blocs, suggests Representative Steve Israel, a centrist from Long Island who is retiring this year. Mr Sanders never faced the “scouring light” of media scrutiny, notes Senator Cory Booker of New Jersey, delicately: “we don’t know” how he would have done.

Had Democrats owned a crystal ball and known in advance that Mr Trump would be their opponent they might have beaten him by picking a different mainstream candidate, for instance Vice-President Joe Biden. But Mr Sanders would have faced months of attack ads, running something like this. “Radical Bernie Sanders doesn’t like America. That’s why he backs tyrants who hate our freedoms [the screen shows old quotes from Mr Sanders praising Fidel Castro of Cuba]. It’s why he wants to make us like bankrupt, failed Europe, with open borders and amnesty for illegal aliens [images of refugees in the Mediterranean, terror attacks in Belgium and France, then Sanders quotes comparing America unfavourably with Denmark]. He wants government-run health care [viewers see a shabby hospital], abortion on demand and welfare for all. Who’d pay for this? You would, with some of the biggest tax hikes in our history. Bernie Sanders, a danger to America.” A third senior Democrat succinctly calls talk of Mr Sanders winning a general election “insane”.

Populist politicians are gaining ground across the democratic West. But in Britain, France, Germany, Poland, Hungary and the Nordic countries so admired by Mr Sanders, the most successful anti-elite movements are broadly of the right, not the left. Even in Greece, where radical leftists hold power, soak-the-rich populism is allied to nationalist resentment at foreigners causing austerity.

This is no accident. To simplify, populists of the left talk about fairness: an abstract idea. They call for government to break up big banks, make sure the rich pay taxes or erect tariff or regulatory barriers to keep globalisation at bay. Populists of the right happily borrow leftish lines about putting domestic workers first, and curbing the might of international finance. But then instead of talking about fairness, they talk of safety and control, of defending precious values that are under assault, and of keeping The Other at bay. Rather than fixing the system, they talk of taking their country back. If it suits their needs, populists of the right will present government itself as an agent of tyranny. Those are potent slogans that appeal to the gut, not the head—and in America just helped Republicans to elect a billionaire who calls tax-avoidance “smart”. They are reasons why the centre-left should beware of choosing to fight the right on populist ground.

If you can’t beat ’em, don’t join ’em

The hard lesson of 2016 is that mainstream politicians do not yet have a perfect answer to the demagogues sweeping the West. Mrs Clinton was a clunking candidate who—disastrously—took the Midwest for granted. But her larger problem was that she could not match Mr Trump’s willingness to tell angry workers whatever they wanted to hear, as when he promised to bring back coal-mining jobs, or manufacturing from Asia. Every rich-world politician knows what voters want: to be shielded from competition that they feel is unfair or unbearable, whether from machines or foreigners. But no responsible leader knows how to do that without harming the economy. As Mr Booker says: “You can’t create policy against a microchip.” As they enter a spell in the wilderness, Democrats cannot out-promise Mr Trump. They need to out-think him, by finding policies that work in the real world, in ways that voters can touch and feel. They have four years.