How is that, pray tell? Here's the argument:
The Joker's makeup in "Dark Knight" — the latest film in a long franchise that dramatizes fear of the urban world — emphasized the wounded nature of the villain, the sense that he was both a product and source of violence. Although Ledger was white, and the Joker is white, this equation of the wounded and the wounding mirrors basic racial typology in America. Urban blacks — the thinking goes — don't just live in dangerous neighborhoods, they carry that danger with them like a virus. Scientific studies, which demonstrate the social consequences of living in neighborhoods with high rates of crime, get processed and misinterpreted in the popular unconscious, underscoring the idea. Violence breeds violence.
Superimpose that idea, through the Joker's makeup, onto Obama's face, and you have a subtly coded, highly effective racial and political argument. Forget socialism, this poster is another attempt to accomplish an association between Obama and the unpredictable, seeming danger of urban life. It is another effort to establish what failed to jell in the debate about Obama's association with Chicago radical William Ayers and the controversy over the racially charged sermons of the Rev. Jeremiah Wright.
Joker = "urban" = "inner city" = black. True, he's white, Heath Ledger is white, but ... But what exactly? All references to white "urban" criminals are actually secretly to blacks? The references to William Ayers were, too?
Also, if we're looking for supposed racial connections here, wouldn't the Socialism reference cut the other way? Karl Marx, François Mitterand, Bernie Sanders, no? Or does even Socialism (which to Americans is mostly a European phenomenon, with pockets of support among mostly white prominent American liberal academics) still become black when coupled with the Joker — who is white but of course black because he's urban and a criminal?
Quite an argument, it seems to me. Thanks to Jules Crittenden for the pointer.