MOBILE, Ala.  The McCain campaign’s depiction of Barack Obama as a mysterious “other” with an impenetrable background may not be resonating in the national polls, but it has found a receptive audience with many white Southern voters.

In interviews here in the Deep South and in Virginia, white voters made it clear that they remain deeply uneasy with Mr. Obama  with his politics, his personality and his biracial background. Being the son of a white mother and a black father has come to symbolize Mr. Obama’s larger mysteries for many voters. When asked about his background, a substantial number of people interviewed said they believed his racial heritage was unclear, giving them another reason to vote against him.

“He’s neither-nor,” said Ricky Thompson, a pipe fitter who works at a factory north of Mobile, while standing in the parking lot of a Wal-Mart store just north of here. “He’s other. It’s in the Bible. Come as one. Don’t create other breeds.”

Whether Mr. Obama is black, half-black or half-white often seemed to overshadow the question of his exact stand on particular issues, and rough-edged comments on the subject flowed easily even from voters who said race should not be an issue in the campaign. Many voters seemed to have no difficulty criticizing the mixing of the races  and thus the product of such mixtures  even as they indignantly said a candidate’s color held no importance for them.