Martin Luther King didn’t die an American hero. By the time of his assassination in Memphis in April 1968 he had lost the support of a majority of African Americans and had been deserted by almost all the white liberals who had backed the civil rights movement

Little of this will be spoken aloud on Martin Luther King Day next Monday. Political leaders from Obama across to the obstructionist congressional right will mark the holiday with laudatory speeches hailing his legacy. It’s a safe assumption there will be no editorials looking at the reasons his reputation was being rubbished towards the end.

King’s popularity - already in decline from its pinnacle following the “I have a dream” speech at the Lincoln Memorial in Washington four years earlier - had plummeted after his address at the Riverside church in New York on April 4th 1967, a year to the day before his death. His focus at Riverside had been on the war in Vietnam.

King had also lost support by increasingly relating the oppression of African Americans to the plight of the poor of all communities.

At Riverside, he drew a direct line from the killing fields of Indochina to the ghettoes of the US, speaking of “the cruel irony of watching Negro boys and white boys on TV as they kill and die together for a nation that has been unable to seat them together at the same schools.”

Black youngsters were dying at proportionately twice the rate of whites. The rioting classes had answered his pleas for non-violence by pointing to the violence perpetrated in Vietnam. “Their questions hit home and I knew that I could never again raise my voice against the violence of the oppressed in the ghettoes without having first spoken clearly to the greatest purveyor of violence in the world today – my own government.”

That’s the sentence which finally did for his standing with respectable America. “I had a dream” had had the lyrical rhythm and resonance of gospel, a heady evocation of the way the world might be. Riverside reeked of rage and angry near-despair.

His one-time media champions were aghast. Ben Bradlee’s Washington Post commented: “Many who have listened to him with respect will never again accord him the same confidence. He has diminished his usefulness to his cause, to his country and to his people.”

The New York Times declared that he had done a disservice to both the peace and civil rights movements and had “slandered” the US military.

King’s turn towards class politics also contributed to the decline of his influence. Historian Michael Honey wrote of the close associates who had soldiered with him in dangerous regions where Jim Crow still ruled the roost. “They had spent their lives in the civil rights movement and the black church. Now King called on them to organise a new multiracial constituency around class issues among Mexican Americans, Indians, and poor whites as well as African Americans....Almost alone, King had to convince not only the civil rights community and a broader public, but also his own reluctant staff members, that they could organise the poor.”

King had travelled to Memphis to try to energise a faltering strike by sanitation workers. By this stage a national poll indicated that 57 percent of African Americans considered him “irrelevant”, while 14 per cent had no view on whether he was or not.

At a rally on April 3rd, King told the strikers to ignore a ban on a march planned for four days hence, drawing a comparison with the direct action victory in Birmingham, Alabama, four years earlier. That spirit had to be rekindled. “The issue is injustice, the refusal of Memphis to be fair and honest with its public servants, who happen to be sanitation workers. Now we are going to march again...

“We need to go around to these...massive industries and say, ‘God sent us here to say that you re not treating His children right...If you are not prepared to (change) that, we have an agenda that we must follow, and our agenda calls for withdrawing economic support from you.’”

He was shot dead next day as he walked along a balcony at the shabby Lorraine Hotel with an entourage including Ralph Abernathy and Jesse Jackson. Canonisation was under way before the cordite smoke had cleared. Threatening in life, he was once again useful in death, symbol of peaceful moderation of the oppressed at a time of gathering tension.

It is this version of King which will be projected on Monday’s memorial day. The message he was striving to impart in Memphis, of opposition to war abroad and demand for economic justice at home, is as ominous for the establishment today as it was back then. So we don’t heard much about it.