For months, Barack Obama has had the image of an incandescent, golden-tongued Wundercandidate. That image may be fraying now. As smart and credentialed as he is, Sen. Obama is often an indifferent speaker without a teleprompter. He has large gaps in his knowledge base, and is just as likely to dig in and embrace a policy misstatement as abandon it. ABC reporter Jake Tapper calls him "a one-man gaffe machine." Take the Auschwitz flub, where Mr. Obama erroneously claimed last weekend in New Mexico that his uncle helped liberate the Nazi concentration camp. Reporters noted Mr. Obama's revised claim, that...