Republicans are back on the Hill to work on the bill to replace the Affordable Care Act before the August congressional recess, which has now been delayed by Senate Majority Leader Mitch McConnell in order to give more time for negotiations and an eventual vote. Several Republican senators, including Sen. John McCain of Arizona, have expressed doubt their efforts will be successful. The Knowledge at Wharton show on SiriusXM recently took a closer look at the challenges facing the legislation with guests Scott Harrington, a Wharton health care management professor, Katherine Hempstead, a senior adviser at the Robert Wood Johnson Foundation,   and Mary Agnes Carey, partnerships editor and senior correspondent at Kaiser Health News. Here are five key points from their conversation.…