Ezra Klein harks back to the days of yore -- specifically, 2009-2010, when Republicans ardently insisted the individual mandate was a tax. Obviously, "tax" is a stigmatized word in American politics, so the health care reform debate was characterized by terminological opportunism, with Republicans insisting the individual mandate was a tax -- it made people who don't purchase health insurance pay money to the federal government, which is a lot like making people who purchase cigarettes pay money to the federal government -- while Democrats insisted it wasn't.
Nobody placed any particular importance on this routine bout of wordplay. But then, after the passage of the Affordable Care Act, Republicans turned to the courts to overturn their legislative defeat. Their legal argument required shutting down each of the several Constitutional authorizations for the individual mandate, one of which is Congress's authority to tax. Suddenly, the two parties flipped positions: Democrats insisted the mandate was a tax, and Republicans insisted it wasn't. (What do I think? I think the merits are murky.)
The rulings overturning the individual mandate cited the Democrats' rhetoric during the debate as proof that the individual mandate was not a tax. Judge Vinson wrote that it would be unfair for Democrats to get away with denying the mandate was a tax in order to get it passed, and then claiming it was a tax to get it upheld in court:
Congress should not be permitted to secure and cast politically difficult votes on controversial legislation by deliberately calling something one thing, after which the defenders of that legislation take an “Alice-in-Wonderland” tack and argue in court that Congress really meant something else entirely, thereby circumventing the safeguard that exists to keep their broad power in check.
But, of course, it's equally unfair for Republicans to fight the law in Congress by calling it a tax and then overturn it in court by insisting it's not.
Now, the bigger picture fact is that it's silly for courts to deem political rhetoric legally binding this way. Hypocrisy isn't illegal. But if you're going to apply this standard to political rhetoric, it ought to apply both ways.