Stuart Taylor, a judicious analyst of legal matters, says (in National Journal) that the Supreme Court probably would uphold the constitutionality of the mandate, for two reasons: Because uninsured people create substantial economic effects by seeking free care from emergency rooms. And because the mandate is, in Congress' judgment, "necessary and proper" for financing health care reform.
But if any activity, or inactivity, can be declared to have economic consequences, then anything can be regulated -- or required. Furthermore, judicial review, and the Constitution itself, is largely nullified by a doctrine of virtually unlimited judicial deference to Congress' estimates of what is "necessary and proper" for the regulation of commerce.
If Congress does something beyond its constitutional powers, that something does not become constitutional merely by Congress saying it is necessary for this or that.
Taylor also says that the alternative to upholding the mandate is for the court to strike down a president's "signature initiative -- something that no court has done in 70 years, for good reason." The reason is a general duty to respect government decisions arrived at democratically. Which brings us to what conservatives must believe in order to believe that the Supreme Court should declare the insurance mandate unconstitutional.
Judicial review -- let us be candid: judicial supervision of democracy -- troubles people who believe, mistakenly, that the Constitution's primary purpose is simply to provide the institutional architecture for democracy. Such people believe that having government by popular sovereignty is generally much more important than what government does; hence courts should be broadly deferential to preferences expressed democratically. This is the doctrine of those conservatives who deplore, often with more vigor than precision, "judicial activism."
More truly conservative conservatives take their bearings from the proposition that government's primary purpose is not to organize the fulfillment of majority preferences but to protect pre-existing rights of the individual -- basically, liberty. These conservatives favor judicial activism understood as unflinching performance of the courts' role in that protection.
That role includes disapproving congressional encroachments on liberty that are not exercises of enumerated powers. This obligatory engagement with the Constitution's text and logic supersedes any obligation to be deferential toward the actions of government merely because they reflect popular sovereignty.
The latter kind of conservatives are more truly conservative than the former kind because they have stronger principles for resisting the conscription of individuals, at a cost of diminished liberty, into government's collective projects. So a constitutional challenge to the mandate serves two purposes: It defies a pernicious idea and clarifies conservatism.