BTW, if you want the source for this statistic, let me know and I will dig it up for you.
But there was one tide that ran in his favor. The country was ready for change. Eisenhower sensed it, and then he caused it.
He went after the black vote by advertising in African-American newspapers, making a highly visible visit to Harlem and speaking out for equal rights. He made inroads among the women's vote. He won the election of 1952 and then emerged from two terms as president as, in the words of retired Princeton political scientist Fred I. Greenstein, a "very analytical and very penetrating figure."
I think after Ike is when the change started. Pre-Goldwater... the republican party basically split the black vote. Most blacks lived in the south, and voted republican. Northern blacks voted for the democratic party. When the dixiecrats joined the republican party in mass in the 60's and 70's, blacks got stuck in the democratic ghetto where they have remained to this day.