Vice President Joseph R. Biden has been filling in for President Obama at speaking engagements recently, including at the National Educational Association annual meeting last week (top), disappointing one of the country's largest unions and the earliest labor group to endorse Mr. Obama. His visits smaller venues such as the Center for Active Seniors during a campaign stop of Davenport, Iowa. (The Quad City Times via Associated Press)

Vice President Joseph R. Biden has been filling in for President Obama at speaking engagements recently, including at the National Educational Association annual meeting last week (top), disappointing one of the country's largest unions and the earliest labor group to endorse Mr. Obama. His visits smaller venues such as the Center for Active Seniors during a campaign stop of Davenport, Iowa. (The Quad City Times via Associated Press)