On one hand, they can't respond to it without looking like a bunch of hypocrites, considering they have carried so much water for Obama for so long.
OTOH, when has that ever stopped them?
It’s an interesting issue. On it’s face, it seems to me to be quite distinguishable from Obama’s situation. Mitt’s great grandparents were U.S. citizens who went to live in Mexico (polygamous Mormons), so it seems American citizenship is established at least as far as Mitt’s great grandparents. Regardless of what Mexican law says about their status, if the U.S. recognizes them as citizens, and since Romney was born in Detroit, I don’t see an issue. Obama’s father on the other hand was never an American citizen. He was either a British subject and/or a Kenyan national, so there’s no way he could confer ‘natural born citizenship’ to his son, regardless of where Barack was born...which has never been conclusively established.