Answer: President Lyndon Johnson

Arizona Senator Barry Goldwater appeared on Meet the Press the Sunday after declaring he would seek the Republican nomination for the 1964 Presidential Election. He would go on to win the nomination and challenge President Lyndon Baines Johnson in the general election. The Meet the Press panelists questioned Goldwater about his views of Johnson's recent policies since he had become President after the assassination of John F. Kennedy.  Despite his famously conservative views, Goldwater avoided attacking the Democratic president directly. He even praised him on some of some of his actions handling the USSR, and did not harshly criticize the Kennedy administration’s controversial use of troops to desegregate public schools. But there was one issue Goldwater could not resist. 

The Senator became more heated as the journalists’ questions turned towards his chances in the general election, which many considered to be slim. He finally attacked the President on the issue of Johnson's claim to the country’s Southern states. MTP  panelist Marianne Means of King Features Syndicate asked,  "Senator, what states in the South do you realistically think you can carry against the first Southerner in the White House in a hundred years?" Goldwater responded that he doubted Johnson was a true Southerner, claiming he changed his tune to suit his constituency: "He is from Texas, and when he is out in my country he talks like a Westerner, and when he is down in Alabama, he says you-all. So I don't know what he is yet."

You can watch Barry Goldwater's 1964 campaign Meet the Press interview in the clip below: