While overall discomfort with an African-American president is much lower, it rises among less-educated whites - the same group that's been a challenge for Obama in the Democratic primaries. Among whites who haven't gone through college, 17 percent say they'd be at least somewhat uncomfortable with a black president; that compares with just 4 percent of white college graduates. Clinton may face a similar problem, however; less-educated whites also are more apt to be uncomfortable with a woman president (21 percent, vs. 7 percent of white college graduates).
39% of Americans said they'd be uncomfortable with president who enters office at age 72, as McCain would, whereas only 16% think same about a female president and only 12% say so about a black president.
I don't think there's any question that questions like this yield a substantial amount of self-censoring among respondents. Social Scientists have a reassuringly unwieldy term for this -- which escapes me at the moment. But basically, many people won't say they'd be uncomfortable with a black president because they know they're not supposed to think like that, even if they do. On the contrary, there's no comparable social stigma associated with thinking that about someone past retirement age.
Still, even with that factored in, that's a very big gap -- and a big slice of the electorate for whom McCain's age is a big issue. No doubt that's why we're hearing a lot of references from Dems about honoring McCain's many decades of service to America.
http://www.talkingpointsmemo.com/So maybe Hillary's argument holds no water!