On April 4 1968, Martin Luther King Jr phoned a local pastor with the title of his Sunday sermon: “Why America May Go to Hell.” The civil rights leader was shot dead before he could address the parishioners of Ebenezer Baptist church in Atlanta. Over the next few weeks the United States found itself on the road to perdition. King’s murder saw the country experience its greatest wave of social unrest since the civil war, with riots in 130 cities. In November of that year, Richard Nixon won a law and order election by stoking the unspoken bigotry that the street violence had done so much to revive. Donald Trump thinks he can do the same with the nationwide protests over police brutality toward African Americans in the wake of the death of George Floyd. But history does not repeat itself, people do.

There are signs that Americans have grown to be significantly better than their previous selves. The protests have drawn wide support from society. Mainly peaceful demonstrations have been a showcase for America’s diversity. Mr Trump’s polling numbers have plunged. Surveys show that voters approve of the protests inspired by Floyd’s death, and strongly disapprove of the president’s response. There has been a sea change in attitudes, with Americans seeming to acknowledge that racism is a real problem for their society. The police officer who was seen suffocating Floyd with his knee has been charged with second-degree felony murder. Confederate statues and other relics to racism have come down in several states.

There is also a long way to the 2020 presidential election. The demonstrations and violence may be a faraway memory by then. The political gaze may be fixed on a second coronavirus outbreak or the failing economy. The chaotic handling of the pandemic has left 100,000 dead and is evidence that Mr Trump is not up to the job. The past is also another country. The unrest today is against a backdrop of depression, deprivation and deep inequality, not the full employment and roaring US economy of the late 1960s. The portents do not look good for a president running for re-election.

The story of American politics since 1968 is dominated by a Republican party that gained a political base through Nixon’s explicit appeals to whites who resented or were opposed to the civil rights movement. Republican leaders went on to weaponise racism to remain in power, which they used to pursue policies that enriched the already affluent at the expense of ordinary workers. Mr Trump’s Republicans are the “white grievance party”. This racism is laced with Trumpian stupidity.

African Americans have been left behind: being black in America, studies show, is like having a criminal conviction in terms of one’s chances of finding employment. Black people often live in the poorest areas and suffer the highest rates of unemployment. Relative to white people, black people receive longer sentences for the same crimes, are treated more disrespectfully by police in routine interactions, and are more likely to be shot by law enforcement. Blacks have long outnumbered whites in US prisons despite representing a fraction of the total population. So stacked is the deck against them that black boys – even rich black boys – can never assume they can escape the poverty trap. This is not a recipe for social comity.

King understood this. His warning in 1967 that the worsening conditions for black Americans must be condemned as equally as riots is still true. “A riot is the language of the unheard,” said King. “Our nation’s summers of riots are caused by our nation’s winters of delay. And as long as America postpones justice, we stand in the position of having these recurrences of violence and riots over and over again. Social justice and progress are the absolute guarantors of riot prevention.” America must do more than listen to the unheard, it must hear them.