NEW YORK, (AP) -- MSNBC was the victim of a hoax when it reported that an adviser to John McCain had identified himself as the source of an embarrassing story about former vice presidential candidate Sarah Palin, the network said Wednesday. David Shuster, an anchor for the cable news network, said on air Monday that Martin Eisenstadt, a McCain policy adviser, had come forth and identified himself as the source of a Fox News Channel story saying Palin had mistakenly believed Africa was a country instead of a continent. Eisenstadt identifies himself on a blog as a senior fellow at...