Susan Estrich, author of The Case For Hillary Clinton, in her latest column, discussing the Bradley effect:

Doug Wilder, who wasn’t elected to the Senate from Virginia, faced the same problem. We who are Democrats would like to believe that race is not a factor in the polling of our party members, but maybe we’re wrong. No one doubts, or at least no one who is honest does, that both racism and sexism come into play as people decide between Clinton and Obama, but could it be that people are more willing to admit that they won’t vote for the woman than that they won’t vote for the black? If this is happening even among us good Democrats, what does that say about Obama’s strength in a general election? Not pretty questions. Not a fair world. But for Democrats who want to win, these are questions that must be addressed.

There’s a unique argument in opposition to Obama: Because Democrats lie to exit pollsters about who they support, the general electorate certainly will, and so Hillary is the safer one to nominate.