Erwin Chemerinsky - Dean of UC Irvine Law School and Professor of Constitutional Law -- and I are on the same page regarding healthcare reform. In a Los Angeles Times op-ed, Chermerinsky argues that Congress has the authority to mandate coverage. I have made the same argument (see here and here).
By contrast, David Rivkin and Lee Casey, two conservative law firm partners, have made multiple arguments challenging the constitutionality of a federal mandate. I have not found any commentary by Constitutional Law scholars which contends that the mandate would violate the Constitution.