The legal case against the Affordable Care Act is completely absurd. You can make the argument sound kind of plausible, but if you’re a law-talking guy, you can selectively cull through precedents and pile assumptions onto each other just so in order to reach pretty much any conclusion you want. That’s pretty much what the legal challenge to the Affordable Care Act would do. As a straightforward interpretation of constitutional precedent, it’s just silly.
Legal analysts are not dismissing the case completely, but that's only because they don’t dismiss the possibility that five Republican-appointed justices will leap at a chance to advance the partisan agenda of their choosing. Jack Balkin, in an article suggesting it’s highly unlikely the law will be found unconstitutional, searches through history and can only find one example of the Court making a ruling so radical and lacking in constitutional basis. It was Pollock v. Farmers' Loan and Trust Company, the 1895 case in which the Court struck down the federal income tax. The reasoning was absurd — the United States had previously used an income tax during the Civil War, and it had been unanimously upheld in 1881.
So, why did the Court rule as it did? It was, Balkin explains, an expression of right-wing fear of economic populism:
The Pollock decision arose out of a political panic among conservatives that swept up the Court along with it. Inequality of wealth accelerated in the late nineteenth century, and a left-wing version of agrarian populism had become a powerful force in American politics. Conservatives believed the rising Populist Party was a genuine threat; they feared the specter of socialism and redistribution of wealth. As Justice Harlan explained:
It was said in argument that the passage of the statute imposing this income tax was an assault by the poor upon the rich, and, by much eloquent speech, this court has been urged to stand in the breach for the protection of the just rights of property against the advancing hosts of socialism.
Well, no need to worry because it’s not like today’s conservatives have been swept up in a blind panic over redistribution! Oh, wait.