WASHINGTON -- Sen. Hillary Rodham Clinton won the most delegates in Pennsylvania's Democratic primary.

Clinton won at least 80 of the 158 delegates up for grabs in Tuesday's contest, according to an analysis of election returns by The Associated Press. Sen. Barack Obama won at least 66, with 12 still to be awarded.

The final delegate count was delayed because many of Pennsylvania's counties are split into multiple congressional districts. Pennsylvania awards delegates according to the statewide vote as well as the vote in individual congressional districts.

Up-to-the-minute: PA Primary Results

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Election officials were expected to continue working Wednesday to assign votes from split counties to the appropriate congressional districts.

In the overall race for the nomination, Obama led with 1,714.5 delegates, including separately chosen party and elected officials known as superdelegates. Clinton had 1,589.5 delegates, according to the AP tally. It will take 2,025 delegates to secure the Democratic nomination.

Analysis: PA was must-win for Clinton

Obama began the night with a delegate lead of 1648 1/2 to 1509 1/2, out of 2,025 needed to win the nomination.

"I think a win is a win. Maybe I'm old fashioned about that," Sen. Clinton told reporters earlier in the day. "I think maybe the question ought to be, why can't he close the deal with his extraordinary financial advantage? Why can't he win a state like this one if that's the way it turns out ... big states, states that Democrats have to win."

Pennsylvania voters enjoyed a rare chance to cast ballots in a meaningful primary late in the campaign season. Registration reached a record level.

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On the Republican side, Sen. John McCain clinched the party's nomination in March.

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.

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