Clinton won this go-round. With 98 percent tallied late last night, she held a solid lead of 10 percentage points, 55-45, and network analysts believed that she would post a net gain of about 15 delegates.
But Clinton's victory - powered by strong support from her core base of white women, older voters and union members, weighted toward western and central Pennsylvania - did little to change a nationwide equation still in Obama's favor.
Obama's strength in the southeastern corner of the state offset Clinton's gains elsewhere and kept her margin in delegates small.
That means that the Illinois senator still has a solid lead nationwide in delegates - up by 132, according to MSNBC - and a half-million lead in popular votes cast, little changed from when this all began back in the wind and frost of mid-March.
Most experts see a growing quandary for the Democrats as they seek to rally behind a candidate to oppose GOP Sen. John McCain in the fall: They don't see how Clinton can win the nomination, yet they don't see what could make her drop out, especially with a Pennsylvania win under her belt.
"One thing about the Clintons is they know that every day matters and something big could happen any day," said Larry Sabato, the University of Virginia history professor and presidential analyst. "Their goal is to stay alive as long as possible."
"The bottom line is that she's won Pennsylvania, and she's going forward," NBC News pundit Tim Russert said on MSNBC last night, minutes after she was declared the winner.
Indeed, the candidates were already starting the next lap of their long-distance race. After crisscrossing Pennsylvania by planes, trains, and buses, Obama had already moved onto the next big battleground state of Indiana last night, before the votes here were even counted.