(NBC News) Martin Luther King Jr’s “I have a dream” speech was a defining moment for the civil rights movement, for America, and for King himself. Fifty years ago this week, King’s soaring words marked a turning point in this country’s long and bitter conversation about race, and earned King a place in history. When we remember Martin Luther King, we remember his dream. It helped awaken an entire nation.

So it’s hard to believe that just over three and a half years after that triumph, King would tell an interviewer that the dream he had that day had in some ways “turned into a nightmare.” But that’s exactly what he said to veteran NBC News correspondent Sander Vanocur on May 8, 1967. In an extraordinary, wide-ranging conversation, King acknowledged the “soul searching,” and “agonizing moments” he’d gone through since his most famous speech.

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