Clinton also was grilled about the ad by MSNBC's Keith Olbermann, one of a series of national television interviews the New York senator gave on Monday.

"Since Senator Max Cleland was cut down by a commercial that featured a picture of bin Laden, that has been _ that tactic has been kind of a bloody shirt for many Democrats," Olbermann said. He was referring to the former Georgia senator and disabled Vietnam War veteran who lost his seat in 2002 after Republicans questioned his willingness to fight terrorism.

Clinton insisted the ad was about presidential leadership, not fearmongering.

"There is nothing at all that is in any way inappropriate in saying, look, presidents face the unexpected all the time," she said. "If you were to hire the person you thought was ready on Day One to do the toughest job in the world, what would you look for? What kind of resume would you be trying to seek out?"

Obama chose a somewhat more lighthearted television venue, chatting up Jon Stewart on Comedy Central's "The Daily Show."

Pennsylvania's demographics suit Clinton. The state has a higher median age, a higher percentage of whites, a lower median household income and fewer bachelor's degrees than the country overall. These are the voters _ working-class whites and voters older than 50 _ who have flocked to her in past contests.