Clinton won at least 82 of the 158 delegates up for grabs in Tuesday's contest, according to an analysis of election returns by The Associated Press.
Obama won at least 73, with three still to be awarded.
Obama limited Clinton's delegate gain by doing well in the Philadelphia area, which was rich with delegates because of the way Pennsylvania apportions them among congressional districts.
Like all Democratic contests, Pennsylvania awarded delegates proportionally, based on the statewide vote as well as the vote in individual congressional districts. Pennsylvania divvied up congressional district delegates based on Democratic voting strength in the most recent presidential and gubernatorial elections.
That resulted in congressional districts in the Philadelphia area with seven or nine delegates at stake. Other districts in more rural parts of the state had three, four or five delegates at stake.
Clinton dominated the state outside the Philadelphia area, winning 60 of 67 counties in unofficial returns.
The final delegate count was delayed because many of Pennsylvania's counties are split into multiple congressional districts. Election officials were working on Wednesday to assign votes from split counties to the appropriate congressional districts. Some counties didn't expect complete results until Thursday or Friday.
In the overall race for the nomination, Obama led with 1723.5 delegates, including superdelegates. Clinton had 1592.5, according to the AP tally.
It will take 2025 delegates to secure the Democratic nomination. Obama picked up two superdelegate endorsements on Wednesday and Clinton picked up one. Superdelegates are the party and elected officials who automatically attend the convention and can support whomever they choose, regardless of what happens in the primaries and caucuses.
The delegate breakdown: Pledged delegates won in primaries and caucuses: Obama, 1488.5; Clinton, 1333.5.
Superdelegates: Obama, 235; Clinton, 259.
The AP tracks the delegate races by calculating the number of national convention delegates won by candidates in each presidential primary or caucus, based on state and national party rules, and by interviewing unpledged delegates to obtain their preferences.
Most primaries and some caucuses are binding, meaning delegates won by the candidates are pledged to support that candidate at the national conventions this summer.
Political parties in some states, however, use multistep procedures to award national delegates.
Typically, such states use local caucuses to elect delegates to state or congressional district conventions, where national delegates are selected.
In these states, the AP uses the results from local caucuses to calculate the number of national delegates each candidate will win, if the candidate's level of support at the caucus doesn't change.
