From the NY Times:

"Just imagine for a moment if it were the black candidate in this election, rather than the white candidate, who was born in Central America, was an indifferent churchgoer, had graduated near the bottom of his university class, had dumped his first wife, had regularly displayed an explosive and profane temper, and had referred to the Pakistani-Iraqi border...

What is happening, I think, is this: religious prejudice is becoming a proxy for racial prejudice. In public at least, it's not acceptable to express reservations about a candidate's skin color, so discomfort about race is sublimated into concerns about whether Mr. Obama is sufficiently Christian.

The result is this campaign to "otherize" Mr. Obama. Nobody needs to point out that he is black, but there's a persistent effort to exaggerate other differences, to de-Americanize him.

Raising doubts about a candidate based on the religion of his grandfather is toxic and profoundly un-American, cracking the melting pot we emerged from. Someday people will look back at the innuendoes about Mr. Obama with the same disgust with which we regard the smears of Al Smith as a Catholic candidate in 1928."