Twice in the past three years, Chief Justice John Roberts Jr. has steered the high court through the highly political maelstrom surrounding the ­federal health care law without its ­rulings being labeled partisan. But new ­challenges to the law and the court lie ahead.

In 2012, the chief justice, joined by his four colleagues on the left, upheld the Affordable Care Act’s critical individual coverage requirement in National Federation of Independent Business v. Sebelius — a constitutional attack on the law. In that case, two justices on the left — Stephen Breyer and Elena Kagan — joined the court’s justices on the right in invalidating the law’s Medicaid expansion. >