“The greatest threat to the health-care overhaul might not be the Supreme Court, which is scheduled to hear challenges to the law next month. Or the shifting alliances of an election year. In the end, it’s more likely to be a lack of medical providers. If the law succeeds in extending health insurance to 32 million more Americans, there won’t be enough doctors to see them. In fact, the anticipated shortfall of primary-care providers, by 2015, is staggering: 29,800.”