You have to go some way back to find a US president entering his last year without having been written off as a lame duck. Barack Obama stands little chance of enacting anything dramatic before he leaves office. But he has had years to get used to that. His abiding setback came in 2010 after Republicans took control of the House of Representatives. Little has passed since then. Yet Mr Obama’s closing months have a potential that is missing from most tail-end presidencies. US society is far more bitter and deeply polarised than when he took office. For those who can still recollect, Mr Obama’s original promise was to heal those divisions. He still has 12 months to make good on it.

The US president can be as withering as any about Donald Trump’s outrageousness. But it is like shooting fish in a barrel. Ridiculing Mr Trump only reinforces his support. The more ignorant — and prejudiced — Mr Trump is shown to be, the more his supporters enjoy raising their middle finger. The goal must be to separate Mr Trump from his fans. The first is a huckster of epic proportions. The second are America’s left behind demographic. More than half lack a college degree and feel deep economic insecurity. Rightly, or not, they also feel mocked. It is no use kicking a section of society when it is down and expecting it to see the light. The tone needs to change. Mr Obama could set the lead on that.

It is tempting to say they are on the wrong side of history. America’s first black president looks likely to be succeeded by its first woman. Why appease those who feel alienated by the march of progress? For two reasons. First, without a sea change in US politics, Hillary Clinton’s agenda is unlikely to fare better than Mr Obama’s. True, Mr Obama pushed through healthcare reform in his first term and enacted a stimulus that saved the US from a deeper recession. But he has done little since then.