It can't be experience. It can't be issues.
I think the reason that "experience" and "issues" seem like pretextual reasons ( <link> ) for Democrats defecting to McCain is that, as the blog post points out, Obama and Clinton's experience are not drastically different and their stances on the issues are almost identical.
Clinton has two more years of experience in the U.S. Senate, but she lacks Obama's State level experience.
And it's difficult for me to come up with major policy differences between the two. Clinton supported mandatory healthcare coverage for children and adults. Obama did not require that such coverage be mandatory for adults. Other than the gas tax holiday, I can't think of any other major (if you call that major) policy differences between the two.
So it seems to many Obama supporters that since it's probabaly not experience and issues that are making Clinton supporters defect, then it must be some other significant reason that is being unstated.
Maybe some women feel scorned by the Obama camp. Maybe some people just don't like Obama. Maybe his personality rubs them the wrong way.
Or maybe the reason that people are defecting is because they feel uncomfortable with the idea of a Black president. This reason seems likely to many of us, because it would explain why defectors' reasoning seems so flimsy.