But they did not present any definitive new evidence that would compel Democratic Party elders to step in and anoint Clinton as their White House nominee, particularly when Barack Obama continues to lead in the overall delegate count and in the popular vote.
Instead, despite a grueling and often bitter campaign, Clinton's victory Tuesday left in play the same questions that remained seven weeks ago after her 10-point victory in Ohio, another large and politically important industrial state.
What does it portend for the fall campaign that Obama is not winning working-class whites, a crucial swing voting bloc, in the Democratic primaries? Or that he has lost most of the biggest states to Clinton?
How much credit should the party elders -- the superdelegates who are expected to select the nominee by providing the final votes needed for victory -- give Obama for drawing new voters to the polls? Or for energizing younger voters and for spurring massive turnout among African Americans?
Should party leaders worry that Clinton has been all but shut out of the black vote?
The big-state primary in Pennsylvania failed to bring clarity. Now, while a muddled Democratic nominating process enters its fifth month of voting, presumptive Republican nominee John McCain is building his fall campaign, embarking this week on a tour of economically disadvantaged areas that is designed to attract the same working-class voters so coveted by the Democrats.
"She can't win but won't quit," Democratic strategist Jim Jordan said of Clinton. Obama, he said, "is going to win but can't close it out. And meanwhile, McCain skates on, unmolested."
The Democrats' indecision pushes the next important test to May 6, when Indiana and North Carolina hold primaries.
Obama is expected to win in North Carolina, with its heavy concentration of black voters, college students and upper-income whites, who have formed a durable coalition for him in the primaries and caucuses.
But Indiana, a predominantly white state with industrial workers and rural voters, is a more substantial test, largely because it presents Obama with another chance to show that he can do better with those blue-collar voting groups that eluded him in Ohio and Pennsylvania.
While Clinton celebrated her win Tuesday night in Philadelphia, Obama demonstrated his immediate focus on Indiana by traveling there and delivering his speech from Evansville. A recent Los Angeles Times/Bloomberg poll showed him holding a slight lead there.
"It would be symbolic if Sen. Obama won a state like Indiana," said the state's Democratic chairman, Dan Parker, a Clinton supporter.
But an Obama loss in Indiana might give Clinton an air of momentum, particularly because it is a state where many Democrats have known Obama for several years because of shared media markets with his home state of Illinois.
Later primaries in West Virginia and Kentucky, which play to Clinton's demographic strengths, might give superdelegates even more reason to reassess Obama's electability.
Until voters in those states weigh in, Obama is likely to point to favorable evidence from the Pennsylvania results in seeking new endorsements from superdelegates.
Obama outspent Clinton on television and radio ads in Pennsylvania by more than 2 to 1, yet he did not make major gains among working-class white voters. But he didn't lose support among that group, either -- even after navigating some of the worst weeks of the campaign so far, including a crisis over racially charged comments by his former pastor and accusations that his own comments about economically "bitter" small-town voters showed him to be elitist.
Media exit polls showed Obama winning 38% of the white vote in Pennsylvania, nearly unchanged from the 34% he won in Ohio seven weeks ago.
Even though he lost Pennsylvania by a substantial margin, Obama may argue that he was able to improve his standing with important parts of the electorate. Exit polls found that he won 37% of voters over age 65, up from 26% in Ohio.
He made modest gains among white men, taking 44% of that vote, a gain of 5 points compared with Ohio.
And while self-described independents were less important in Pennsylvania than in Ohio, Obama won a larger share of that group Tuesday.
Obama's campaign is likely to use these numbers in his arguments to superdelegates, some of whom worry that, if nominated, he might not withstand attacks from Republicans aimed at making voters uneasy with his unusual background and lack of experience in federal government.
But as both Democrats fight on, and as about 250 out of the nearly 800 superdelegates remain uncommitted, many strategists and leaders fret that a protracted campaign can only hurt the party's chances of beating McCain in the fall. In the six-week Pennsylvania campaign, Obama faced new scrutiny for certain comments and past relationships, while Clinton was caught exaggerating the dangers she faced in a trip to Bosnia as first lady in the 1990s.
And Pennsylvania's results showed that a potentially damaging racial divide persists in a campaign that once focused on voters' excitement over electing either the first black or female president.
Clinton won just 11% of the black vote.
"Anybody who says past this point that this is good for the party or good for the nominee is a fool," said Jordan, the Democratic strategist, who is not affiliated with either campaign. The candidates, he said are "exhausted, they're more likely to make mistakes, and they're raising each other's negatives."
Evidence of the damage was clear in the exit polls. Consider one example sure to be troubling to Democratic leaders as they examine their chances for November: Among primary voters, about 4 in 10 surveyed said that Clinton was not honest and trustworthy, whereas about 3 in 10 had the same negative assessment of Obama.
© 2008 Los Angeles Times