Hillary Clinton spent the morning in Bethlehem, touting her health care plan. She told supporters her plan would work better than Barack Obama's health plan. "It's no wonder that my opponent has been so negative these last few days in this campaign. Because I think you saw a big difference between us. It's really a choice of leadership. I'm offering leadership you can count on."
While Clinton went after her opponent, Obama attacked Republican John McCain. "I guarantee you when it comes to November people will be unified because they know we cannot afford a third George Bush term, and that's what John McCain is offering, a third George Bush term."
McCain was not campaigning Sunday, but has long argued Obama has a habit of twisting his words.
Clinton is favored to win Pennsylvania and has vowed to stay into the race until the party's convention in August.
So what happens after Tuesday? Following the primary in Pennsylvania, there are still nine contests up for grabs.
On May 3rd, residents in the tiny Pacific Island nation of Guam will go to the polls. Three days later voters in North Carolina and Indiana will decide.
On May 13th, West Virginia voters will pick who they want as president. That's followed a week later by residents in Oregon and Kentucky.
On June 1st, Puerto Rico residents will head to the polls. And the last primary in the nation will take place on June 3rd. That's when residents in Montana and South Dakota will vote.