Hillary Clinton and Barack Obama scuffled over health care Saturday, revisiting one of the Democratic candidates' few significant policy differences three days ahead of the Pennsylvania primary.

Clinton's campaign mounted a protest after Obama released a TV ad Saturday, to be shown statewide until the primary, criticizing Clinton's health care reform proposal. Clinton's health care plan includes a mandate to buy insurance and offers tax subsidies to help some people purchase it.

"What's she not telling you about her health care plan?" the ad asks. "It forces everyone to buy insurance even if you can't afford it, and you pay a penalty if you don't."

In accusing Clinton of wanting to penalize people who don't buy insurance, the ad does not explain how Obama, without penalties of his own, would enforce his proposed mandate that children be covered. Obama's health care plan would not mandate coverage for adults, though, and it would provide assistance that, he says, would make coverage affordable.

Clinton frequently criticizes Obama's approach.

"I just heard that my opponent has put up an ad attacking my health care plan, which is kind of curious because my plan covers everybody and his leaves out 15 million people," Clinton retorted Saturday in York, Pa. "Just leaves them out in the cold - now instead of attacking the problem, he chooses to attack my solution. I don't think that we can just make speeches about this."

Her comments came as the campaign released a statement calling the ad's assertions "false and widely discredited."

By Aaron Bruns and Bonney Kapp of Fox News and The Associated Press, April 19, 2008