Pennsylvania primary

Hillary Clinton and Barack Obama supporters rally outside the National Constitution Centre prior to a debate in Philadelphia Photograph: Jeff Fusco/Getty

Barack Obama arrives at Philadephia International airport on his way to address a rally at Independence Hall. Obama has said it is unlikely he will win in Pennsylvania but he expects to do well enough to cast doubt on Clinton's ability to stay in the race Photograph: Emmanuel Dunand/Getty

Obama and Clinton stand on stage at the close of their Democratic debate in Philadelphia Photograph: Emmanuel Dunand/Getty

Clinton speaks in the rain during a campaign rally at Renziehausen park. After recent defeats in a string of primaries, Clinton must win Pennsylvania by 10 percentage points or more to stay in the race Photograph: Joe Raedle/Getty

Clinton is greeted at a campaign rally at a high school Photograph: Joe Raedle/Getty

Obama waits to be introduced with his wife, Michelle, at a rally at the University of Pittsburgh Photograph: Scott Olson/Getty

Clinton and her daughter, Chelsea, laugh as four-year-old Sonya Wilkerson hides behind her mother's leg at a campaign event, at Haverford College Photograph: Robyn Beck/AFP

Obama meets residents while canvassing for votes in Philadelphia Photograph: Emmanuel Dunand/AFP

A supporter of Clinton Photograph: Robyn Beck/AFP

Obama talks to a little boy called Daniel Van Dusky while they sit at the bar during a visit to the Glider Diner in Scranton Photograph: Emmanuel Dunand/AFP

Clinton celebrates with her daughter Chelsea, to the theme of Rocky, after speaking at a late night rally at the University of Pennsylvania Photograph: Win McNamee/Getty

Obama samples beer made at the Bethlehem Brew Works Photograph: Emmanuel Dunand/AFP

Supporters of Clinton gather for a campaign rally at Market Square, in Pittsburgh Photograph: Jeff Swensen/Getty