HARRIS WOFFORD, the Democratic candidate for US Senate, has received the endorsement of Pennsylvania's two major daily newspapers - the Philadelphia Inquirer and the Pittsburgh Press.Sunday's endorsement by the Press was considered something of a coup as Pittsburgh is the home of Wofford's Republican challenger, former two-term Gov. Dick Thornburgh. Wofford advised Martin Luther King Jr. and President Kennedy, and was a co-founder of the Peace Crops. He was president of Bryn Mawr College and state secretary of the industry. "He has talked to the concerns of ordinary Pennsylvanians," the Inquirer said of Wofford. "He says they count and the government - yes, government - needs to pay attention." Mr. Thornburgh, who served for three years at US attorney general before resigning last August to run for the Senate, conveys no sense of mission, the Inquirer said. "His prescriptions for societal ills remind us of the Reagan administration's response to dirty air: Study it to death." The winner of the Nov. 5 election will fill the remaining three years of the term of the late John Heinz, a popular Republican senator who was killed last April 4 in a plane crash.