Bob Somerby of The Daily Howler objects to the liberal conventional wisdom that, as the New York Times put it, "It is inconceivable that this campaign [birtherism]... would have been conducted against a white president":
We think it was a remarkable statement because somewhat similar campaigns already have been conducted against white candidates. A somewhat similar campaign was conducted in 1988 against Candidate Michael Dukakis, for instance. After that, strains of the same ethnic/nativist cards were played against Candidate Kerry in 2004.
It's a fair point. However, we need to be careful about the comparisons that we make in thinking about this question. As Somerby notes, Obama is different from other presidential candidates on other dimensions than race. In particular, he has a unique life story:
Let’s be clear: No one has ever been slimed in the exact same way Obama has been slimed. Reason? No other Democrat’s life story ever presented the same opportunities. Before Obama, no president or presidential candidate ever had a father from an exotic foreign country; no such candidate had ever been born in our most distant and exotic state.
For Obama's race to be the cause of the birther critique, we would need to believe that a white presidential candidate with a foreign parent who spent much of his childhood overseas would not have his eligibility for office questioned. Is this plausible? Maybe, but I don't think it's "inconceivable" that a similar attack would have been launched at a white Democrat with Obama's background.
None of this is to say, of course, that racial attitudes haven't contributed to the acceptance of the myth among the public. Sadly, there's lots