She was running close to or leading Sen. Barack Obama in the crucial Philadelphia suburbs and was crushing him in southwestern Pennsylvania and the Scranton region.

"Some people counted me out and said to drop out, but the American people don't quit, and they deserve a president who doesn't quit either," Clinton told cheering supporters last night at the Park Hyatt Philadelphia at the Bellevue. "Because of you, the tide is turning."

With the support of Gov. Rendell, Mayor Nutter and much of the Democratic establishment, Clinton had been expected to carry the state, but the better-funded Obama was able to unleash an avalanche of television commercials and shave her lead in opinion polls.

Despite Clinton's win, Obama remains the front-runner for the nomination, with a significant overall delegate lead and a huge financial advantage. She also has few primaries left in which to overtake him.

Still, Clinton's big margins among white working-class voters seemed likely to add fuel to her argument that Obama cannot win the big industrial swing states in the fall against Republican John McCain.

After spending the afternoon in Philadelphia, Obama flew ahead to a rally with rocker John Mellencamp in Indiana, site of one of the next round of primaries May 6. He briefly acknowledged the Pennsylvania results in remarks that focused on Indiana and McCain.

"There are a lot of folks who didn't think we could make this a race when we started," Obama said. "Now, six weeks later, we closed the gap. We rallied people of every age and race and class. . . . We registered a record number of voters, and it is those voters who will lead our party to victory in November."

Voters swarmed the polls, given the chance to have a meaningful say in a presidential nomination for the first time in years.

Commonwealth Secretary Pedro A. Cortes described the turnout as "phenomenal." He said it might reach 50 percent statewide, perhaps eclipsing that of the 1980 primary, when President Jimmy Carter was challenged by Sen. Edward M. Kennedy (D., Mass.) for the nomination.

Hop-scotching the state

The same demographic split prevailed in most of the other contests between Obama and Clinton.

With no other contests on the schedule, the candidates hop-scotched across Pennsylvania for nearly seven weeks, spending $20 million on TV advertising - a bombardment that, for example, featured 228 spots a day in the Harrisburg media market. Obama, his campaign flush with cash, was able to outspend Clinton by a ratio of about 3-1 on the air.

A tough turn

"Who do you think has what it takes?" asked the ad.

Obama has struggled in some states to win over white working-class voters, older voters and Catholics, key parts of the coalition that strategists say a Democrat needs to carry big industrial swing states.

For his part, Obama said that anything less than a blowout win here for Clinton would do little to help her overcome his delegate lead because delegates are awarded proportionally.

Polls showed that Clinton always had the advantage among women, older voters, Catholics, union households, and white voters with high school educations making less than $35,000. Obama was leading among younger voters, African Americans, Democrats with incomes over $75,000, and liberals.

The state seemed demographically tailor-made for Clinton, with higher percentages than the nation as a whole of voter groups that have favored her in past races. Obama was counting on Philadelphia and its suburbs to overcome expected Clinton support elsewhere.

Clinton's campaign had been on the verge of elimination after 11 losses last month before she won popular-vote victories in Ohio and Texas based on her advantage with the working class.