"The middle class is invisible to this president," Clinton said. "He doesn't see how hard it is to make ends meet."
Clinton's visit to the Jewish community center in the far northeastern corner of Philadelphia was the first of two area stops on Monday; she is scheduled to be at a rally in suburban Horsham in the afternoon.
She outpolled Obama in both areas in Pennsylvania's Democratic primary six months ago, when she beat him by 10 percentage points.
Now, Clinton is trying to use her popularity to help the Illinois senator against Republican presidential candidate Sen. John McCain.
Clinton and her husband, former President Clinton, campaigned with Obama running mate Joe Biden on Sunday in Scranton, another area where Clinton did well in the primary.
Earlier Monday, Clinton said Obama is closing in on an Election Day win.
Clinton said in an interview taped for NBC's "Today" show from Scranton that she thinks Obama has substantially improved his chances by the way he has handled questions about the country's severe credit crisis. "I think he's closing it," she said.
