Rejection of the Medicaid expansion would potentially leave large numbers of Pennsylvania's poor uninsured.The marketplaces are envisioned as online stores in each state that function as a way for people to shop for health insurance. Consumers would be able to interact with the marketplace online but could also apply by mail or telephone. The marketplaces will provide both individual and small business coverage. About 1.35 million are uninsured, according to the U.S. Census Bureau. Enrollment to participate in the exchanges is supposed to begin Oct. 1. Under the law, virtually all Americans must carry health insurance starting next year, though most will just keep the coverage they now have through their jobs, Medicare or Medicaid.