And here is Liz's take on that speech:
'I never expected to see Lyndon B. Johnson on the television. I never expected that look on his face that I at once recognized as a sort of resignation. What is this jackass up to, I wondered. When he began to speak I listened despite myself and in the end I was so glad that I did. First he called a partial end to the bombing in Vietnam. This made me turn up the volume a little to see what other surprises were in store for us. Then he began to talk about the national division over the war in Vietnam. And this was the reason he gave for the biggest surprise of the broadcast. Looking at the camera in a moment that conveyed for me, the most emotion of his presidency, he said, “I shall not seek, nor will I accept, the nomination of my party for another term as your president.”This was a moment that we had waited on for so long. He wouldn’t run. There was no possible way that we would have to put up with his insane bureaucratic bullshit for another four years.'
This is an article from the L.A. Times discussing LBJ's possible motivation for bowing out taken from http://articles.latimes.com/2008/mar/30/opinion/op-jones30 :
'Forty years ago tomorrow, President Lyndon B. Johnson shocked the nation with his televised announcement that he would not run for another term as president.