Veteran White House reporter Keith Koffler writes on the blog that people may have forgotten how Martin Luther King vilified and controversial and that nobody was more despairing at times.

Noting that Mr King now has his own memorial on the Mall in D.C, Mr Koffler writes: 'There was a decade that followed the great successes of Birmingham and Selma in which he was just struggling, fighting the good fight, and scorned, and many folks angry.

'But what he understood, what kept him going, was that the arc of moral universe is long but it bends towards justice.'