Pennsylvania Primaries (19 images)

Democratic presidential candidate Sen. Hillary Clinton laughs as she addresses supporters in Market Square in downtown Pittsburgh April 21, 2008 on the eve of the Pennsylvania Primary election. (UPI Photo/Archie Carpenter)

Democratic Presidential candidate Hillary Clinton talks with voters waiting to vote at a polling place in Conshohoken, Pennsylvania, on April 22, 2008. She was making some last minute campaign stops as voters went to the polls for the Pennsylvania Primary. (UPI Photo/John Anderson)

A supporter for Sen. Barack Obama cheers as the rally at the Peterson Event Center starts in Pittsburgh on April 21, 2008, the eve of the Pennsylvania Primary election. (UPI Photo/Archie Carpenter)

Democratic Presidential candidate Barak Obama waves from the back of his campaign train to a large crowd that tuned out for him at the Wynnewood Rail Station Whistle Stop in Wynnewood, Pa. April 19, 2008. Hundreds turned out to listen to Obama who is on a train whistle stop campaign across Pennsylvania this weekend. The Pennsylvania Primary is scheduled for April 22, 2008. (UPI Photo/John Anderson)