To overtake Barack Obama in the nationwide popular vote, Hillary Clinton needs a bigger win in tomorrow's Pennsylvania primary than she has had in any major contest so far. And that's just for starters.
After more than 40 Democratic primaries and caucuses, Obama, the Illinois senator, leads Clinton by more than 800,000 votes. Even if the New York senator wins by more than 20 percentage points tomorrow -- a landslide few experts expect -- she would still have a hard time catching him.
Clinton needs ``blowout numbers,'' says Peter Fenn, a Democratic consultant who isn't affiliated with either campaign. ``The wheels would have to come off the Obama bus, and the engine would have to blow.''