HARRISBURG, Pa., April 22 (UPI) -- The six-week build-up to Tuesday's Pennsylvania primary culminated in an ad campaign by Sen. Hillary Clinton questioning her rival's ability to lead.

Against a backdrop of images of Pearl Harbor and bin Laden' title='Osama bin Laden' class='tpstyle'>Osama bin Laden, Clinton, D-N.Y., asked voters not to "take a leap of faith or have any guesswork" when casting their ballots, The New York Times (NYSE:NYT) reported.

Campaign officials from Sen. Barack Obama, D-Ill., said the television ads were using "the politics of fear."

Several polls show Clinton leading Obama in Pennsylvania's primary, with 158 pledged delegates at stake.

In an interview Monday with Larry King on CNN, Clinton said the ad addressed the idea that "that the new president will inherit some of the most dangerous and difficult decisions that any president has had to make in a very long time."

"I want people to think seriously about leadership because that's what I'm offering in this campaign," she said.

Bill Burton, a spokesman for the Obama campaign, said Clinton invoked bin Laden "to score political points. We already have a president who plays the politics of fear and we don't need another."