At the heart of the legal showdown over the Affordable Care Act are questions of governmental power: How broad is Congress's authority to regulate interstate commerce, and does it extend to an individual's health care choices and the private insurance market? Can Washington unilaterally double the size of Medicaid, which is funded partly by the U.S. Treasury but run by the states? On the line, in the middle of an election year, is the President's key domestic-policy achievement. The Supreme Court proceedings begin March 26 and will last three days. A ruling is expected in late June.
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