Watching the debate I noticed that Biden referred to the Muslim population of Bosnia and Herzegovina as "Bosniaks". This is actually the correct term, though in English people often say simply Bosnian Muslims. When he said it, the first thing I though was, I wonder how many right-wingers would jump on this as a gaffe on the model of candidate George W. Bush's reference to 'Grecians.'
I don't know who else exposed their own ignorance by falling into this trap. But Cokie Roberts did.