Barack Obama and Hillary Rodham Clinton hit each other with TV attack ads in the final days before the critical Pennsylvania primary, notching up the animosity in the Democratic presidential campaign on the eve of Thursday's nationally televised debate.
With Clinton trailing in delegates and 11 points behind in a new national poll, she faces Obama in Philadelphia on Thursday for what could be the climax of an extremely contentious few days.
The former first lady has labelled Obama an elitist for remarks he made about bitterness among economically hard-pressed working class voters. The first-term Illinois senator has countered with charges that Clinton was pandering by drinking a shot of whiskey in front of TV cameras and with stories of learning to shoot a gun at her father's knee.
But, in campaign appearances on Tuesday, the candidates sidestepped opportunities to deepen their conflict, leaving the tough talk to their advertisements.
Clinton's new ad pulled together a string of sound bites from Pennsylvania voters who chastised Obama for his remarks that Pennsylvania's working class was clinging to guns and religion in bitterness over job losses and falling living standards.
Obama's ad shows Clinton being briefly heckled as she criticised Obama at a Monday gathering of the Alliance for American Manufacturing. The ad concludes with Obama accusing Clinton of playing the "politics of division and distraction."
The heat in the Democratic race reflects the view that Clinton must score a sizable victory in the Pennsylvania primary on Tuesday to keep her candidacy alive. She trails Obama 1,640-1,504 in delegates with only 10 state primary and caucus votes remaining after Pennsylvania, the largest state still to vote.