JOHNSTOWN (AP) _ Hillary Rodham Clinton and Barack Obama swapped some of the most negative attacks of the campaign two days before the Pennsylvania primary, each unleashing television ads Sunday that accused the other of maintaining ties to special interests they both claim to reject.

Obama also paid the Republican presidential nominee-in-waiting a backhanded compliment. "Either Democrat would be better than John McCain," he told an audience in Reading. "And all three of us would be better than George Bush."

That drew a rebuke from Clinton, who said, "We need a nominee who will take on John McCain, not cheer on John McCain."

With the Republican nomination long since secure, McCain reported his best fundraising month of the campaign, and criticized both Democrats for advocating higher taxes that he said would worsen any recession.

But he seemed more eager to criticize the front-runner, Obama, more than the former first lady. Obama's relationship with former 1960s radical William Ayers is "an open question," McCain said on ABC's "This Week." Without being asked, he said Obama had become friends with Ayers and "spent time with him while the guy was unrepentant over his activities as a member of a terrorist organization."

Ayers, an education professor, has been quoted in an interview as saying, "I don't regret setting bombs" decades ago. Obama has said Ayers lives in his Chicago neighborhood, but that they do not speak regularly.

Two days before the Pennsylvania primary with 158 delegates at stake, Obama and Clinton observed the rituals of Sunday campaigning: a visit to church, stops at restaurants catering to families, as many public events as possible.