Medicaid is already the nation's largest health insurance program in terms of number of people covered: It serves nearly 1 in 5 Americans. Yet at the same time it's putting increasing strain on the budgets of states, which pay about 40 percent of its costs.
The Affordable Care Act survived a near-death experience at the Supreme Court earlier this year. And the overhaul law's fate again hangs in the balance come Election Day. Mitt Romney has vowed to work for its repeal, if he's elected president.