Hillary Clinton tells supporters she is no quitter as she celebrates her widely predicted victory over Democratic rival Barack Obama in the state of Pennsylvania.
Mrs Clinton has won most of the big state contests but still trails in the delegate count and in the total votes cast. The state's Democrats voted for the person they want to run for president.
Mr Obama had predicted he would lose the state but said he made strides in reducing Mrs Clinton's initial lead. He rejects her claim that he could not win the big swing states in November's election.
The former first lady told cheering supporters at a victory rally in Philadelphia that she had beaten a "formidable opponent" who had outspent her three-to-one.
Illinois senator Mr Obama had shattered campaign spending records in Pennsylvania as he sought to floor the former first lady with a knockout blow.
But the state's demographics - with plenty of blue-collar, white and older voters - once again proved ideal for Hillary Clinton.
Polling stations in Philadelphia included a private garage. The tight contest has prompted 200,000 people to register as Democratic voters this month and spurred high turnouts in the primary.