(BusinessWeek) Nixon couldn’t do it. Clinton couldn’t do it. But on Mar. 23, after decades of debate, lobbying, and political wrangling, Barack Obama signed health reform into law. What does this new mandate mean for individuals, companies, and the health-care industry? On Mar. 24, I talked with one of the executives on the firing line, Chairman and CEO Ron Williams of Aetna (AET), which provides health-insurance benefits to more than 36 million Americans.