Democratic presidential hopefuls Barack Obama and Hillary Clinton are in Pennsylvania, which holds the party's next nomination contest April 22.
Both candidates are set to take part Monday, in a forum on manufacturing, in Pittsburgh.
Later, Obama will address the annual meeting of the board of directors of The Associated Press in Washington, D.C. Presumptive Republican nominee John McCain is also scheduled to speak at the event.
On Sunday, the Democratic rivals continued sparring over comments Obama made last week in San Francisco. He had argued that small town voters cling to issues such as guns or religion because they are bitter about the poor economy.
Clinton attacked Obama for the remarks, accusing him of elitism. McCain also denounced his comments as elitist.
Obama fired back at both Clinton and McCain, saying they are out of touch if they do not think voters are bitter about the U.S. economy.
Clinton has long been heavily favored to win Pennsylvania easily, but recent opinion surveys indicate her lead over Obama has narrowed during the past six weeks. The two Democratic senators are competing to win the party's presidential nomination for the U.S. general election in November.
Some information for this report was provided by AFP, AP and Reuters.