CARROLL, Iowa—Waiting for Martin O’Malley to arrive for a backyard campaign stop, Chris Henning and some of her friends tried to figure out which office the Democratic presidential candidate once held. Was he governor of Maryland, or perhaps Virginia? They weren’t sure.

Another Iowan who came out to hear Mr. O’Malley speak was at a loss as to his employment. “He’s from the East Coast,” Rosemary Partridge told a reporter. “Connecticut? I’m trying to guess. He’s a senator.”

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