Had he lived, Martin Luther King would now be an elder statesman of American politics, having given further service to his country through continued moral leadership and probably through holding high office.

Today, aged 89, not an impossible age, he would doubtless remain the magisterial voice of tolerance and reason he was before his assassination half a century ago.

It is not true that America needs such an influence on its national life more than ever, because King was needed more than ever when America stood on the brink in the 1960s. Since he led the struggle for human rights in those years, much obvious and genuine progress has been achieved, even if it is sometimes taken for granted.

Before the Civil Rights Act and the Voting Rights Act were passed by 1965, the position of black Americans in the South and even some northern industrial cities resembled the apartheid society of South Africa. Formal and petty discrimination was found in areas such as public transport until Rosa Parks and others decided that they were not going to be forced to sit at the back of the bus. Bars, clubs and even drinking fountains were rigidly racially segregated. Gerrymandering and restrictive franchise rules effectively guaranteed minimal black representation at local, state and federal levels. The Supreme Court, until the 1950s, upheld the pernicious doctrine of “separate but equal”.

Informal social and economic discrimination was just as destructive in the age before King made a difference. Discrimination in housing, education and employment was far more common than today.

So that was the world King helped to change. Unlike Malcolm X, the Black Panther Party and Nation of Islam, he did it through a commitment to the American ideal, national unity and a rejection of black separatism. His cause was morally driven by a manifest historic injustice. In his “I Have a Dream” speech in 1963, King, speaking on the steps of the Lincoln Memorial, said that the promises made by Abraham Lincoln for emancipation and equality had not been kept. He, King, the quarter of a million people in his audience and many more millions beyond Washington were there to make sure that, at last, the “promissory note”, the cheque written a century before, was going to be fully honored.

In his last address in 1968, on the day before he was slain in Memphis Tennessee, he, prophetically, said that he might not live to see the “promised land”.

Though he helped it happen, he did not live to see the first black US ambassador to the United Nations (1977), the first Black governor of a state since the civil war (1990), nor Colin Powell and Condoleezza Rice becoming secretaries of state and Barack Obama become president in the 2000s. Today’s prominent African Americans in politics, law, academia, business and culture, and the emergence of a solid black middle class would have made King proud, and vindicated his peaceful approach.

Still, Trump’s America is hardly the promised land. The president, in stark contrast to his Republican and Democrat predecessors, has appointed relatively few black Americans to high profile roles in his administration or as judges, for example. The White House hasn’t been this white in decades; while there have never been more black Americans ready to fulfil senior roles. Indeed, with the departure in February of Omarosa Manigault-Newman from the West Wing there are no senior African American women in the White House. Ms Manigault-Newman complained that “I have seen things that have made me uncomfortable, that have upset me, that have affected me deeply and emotionally, that has affected my community and my people”.

It sets a poor example. Today some southern states are starting to erode the equal voting opportunities that were so hard won, introducing bureaucratic obstacles to registration and voting that will reduce turnout among ethnic minorities and the legitimacy of elections. It is difficult to believe it is happening.

In the world dreamt of by King there would be no need for the Black Lives Matter movement, because the ingrained racism that incubates such attitudes and such violence would have been eradicated. King would also have been right there, campaigning to remove those symbols of oppression that still litter the southern states, taking confederate imagery in flags and statuary out of the official sphere. He would have done so with grace and massive moral authority.

It is almost surreally hypothetical, but even a man of King’s vision might find it difficult to imagine that General Lee statues and the old confederate flag would be expunged from state houses in Georgia and Alabama – which is a measure of the changes he wrought, glacial though the pace of progress has been. He would no doubt have been astounded to have learnt a federal holiday would be named after him: he concentrated on the practical work of bringing America’s people together.

Contrast that with bombastic President Trump’s crass remarks equating peaceful protesters with neo-fascist thugs at the Charlottesville disturbances in Virginia last autumn. Whoever the 8 per cent of black Americans who voted for Trump in 2016 may be, one can only hope they were armed with low expectations.

Where King preached a gospel of tolerance, peace and inclusiveness in the best American tradition, the Trump phenomenon is hideously white, resentful, scapegoating and divisive. The president gives the impression that the interests of African Americans are not a priority for him, even though that cheque King talked about in 1963 is yet to be fully honoured. Trump’s views on Mexicans are blatantly racist: he has wondered aloud why America couldn’t have more migration from Norway. Where King dreamed a noble dream, Trump wants to deport the modern day “dreamers”. Self parody was never so depressing.

It is almost as if the president thinks that black votes don’t matter, nor national cohesion, nor human rights. The memory and the words of King echoing down the decades should remind him why he is wrong about all of that, as with so much else.

–independent.co.uk