Before the Storm: Barry Goldwater and the Unmaking of the American Consensus by Rick Perlstein:
Strom Thurmond was perhaps the most conservative legislator in the Capitol. He was also Barry Goldwater’s friend; when Thurmond broke the filibuster record during the 1957 civil rights debate, Goldwater was the only senator who spelled him for bathroom breaks. Like most of the South’s politically alert demagogues, by 1964 Thurmond had stopped shy of directing scorn at blacks themselves; he proclaimed himself a constitutionalist, pure and simple. Goldwater had no compunctions about asking for Thurmond’s endorsement. It was freely offered. Goldwater then dared Thurmond to go one better and become a Republican. That would make history: the only Republican senator from any state in the old Confederacy was John Tower.
Thurmond asked his cronies about the idea. They told him he was crazy. He polled South Carolina voters. They told him he wasn’t crazy. A third voice tipped the decision: Roger Milliken, Thurmond’s biggest benefactor. And so, in a statewide TV address on September 16, in front of a “Goldwater for President” poster bigger than he was, Senator Thurmond acted as if he had hardly given the decision a second thought. If Lyndon Johnson’s Democrats prevailed, he said, “Freedom as we have known it in this country is doomed.”