When Herman Cain began singing "Amazing Grace" at the National Press Club on Monday, some believed he was trying to distract attention from the sexual harassment charges that had surfaced against him. But, as he explained, "My faith is a big part of who Herman Cain is." In fact, though he's decided to campaign on his background in business, Mr. Cain is an ordained minister and deeply religious man.

Like President Obama, Mr. Cain belongs to a mostly black congregation with a black pastor. But that is where the similarities end. Stark differences between the political philosophies of these two men may be rooted in their profoundly different theological heritages. The churches both men are (or in the case of Mr. Obama, were) longtime members of are known for liberal...