In 1964, John H. Buchanan Jr., a Southern Baptist minister and Goldwater Republican, was elected to Congress as part of the Deep South’s backlash to the civil rights agenda of the Johnson administration. He was one of the first five Republicans, all elected that year, to be sent by Alabama to the House of Representatives in the 20th century.

When he got to Washington, he supported the Vietnam War and school prayer. He voted against Medicare and the Voting Rights Act.

But by the late 1960s, the climate in the nation’s capital was changing faster than that in his hometown, Birmingham, where resistance to desegregation was not only respectable but legal. After Mr. Buchanan joined the integrated Riverside Baptist Church in Washington, his perspective began to broaden.

“When you’re deeply involved in a biracial entity, you think of people as brothers and sisters,” he told The Washington Post in 1976. “Then the denial of rights of my brothers and sisters becomes an infringement of my rights as well.”