Between 1948, when American National Election Studies first surveyed the electorate, and 1970, the percentage of voters who were white didn’t change much, ranging from 89 to 91 percent.

ANES didn’t begin breaking out data on mainline and evangelical Protestants until 1960. Traditional mainline Protestants – including Episcopalians, Presbyterians, Methodists and Lutherans — constituted a decisive plurality of the electorate at 45 percent. Evangelicals stood at 29 percent and Catholics at 20 percent. Only one percent defined their religion as “none.”

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