Obama and Biden greet supporters in Illinois Saturday. (AP Photo)
CHICAGO, Illinois (CNN) - Joe Biden made his debut Saturday as the Democratic vice presidential candidate.
Biden, the senior U.S. senator from Delaware, invoked Abraham Lincoln in the 16th U.S. president's home state.
"President Lincoln once instructed us to be sure to put your feet in the right place and then stand firm," said Biden, a native of Scranton, Pennsylvania, whose working-class roots and foreign policy experience Democrats hope will help Obama. "Today in Springfield I know my feet are in the right place and I'm proud to stand firm with the next president of the United States of America, Barack Obama."