It is not. The precedent is around ninety years old, but firmly within modern history. As Franklin Roosevelt attempted to enact his New Deal agenda, the so-called "Four Horsemen", often along with Justice Roberts and/or Chief Justice Hughes, repeatedly ruled against his alphabet agencies and sweeping social bills.
So, Roosevelt worked to find the necessary votes to pack the court. His "Judicial Procedures Reform Bill" was not so different from any of the other "judicial reforms" we've condemned when other strongmen around the world used them to strengthen their power. Politicians from Roosevelt's bloc spewed vitriol at the justices who were simply trying to do their jobs. In Iowa, effigies of the six justices who had opposed any of Roosevelt's actions were found hanged by nooses. Once Roosevelt secured political support and signaled his willingness to push for packing the court, the justices backed down and began ruling in his favor, repeatedly. Where months before it had struck down a New York minimum wage law, a nearly-identical law in Washington was deemed perfectly constitutional. The National Labor Relations Act was fine and dandy. Coal mining was suddenly interstate commerce after all. In fact, the Commerce Clause now covered everything; one clothing factory in Virginia was enough commerce to quality. Later, the court would rule that a man growing wheat for his own consumption was sufficient "commerce" to warrant near-limitless federal rule-making. After all, it meant he bought less wheat from someone else, so clearly it was within the feds' purview. Wickard v. Filburn stands as precedent today. The justices on that court kept their seats but gave up their power.
Now, another populist has shown up. One who has a different vision for the nation than that laid out by the neoliberal technocrats who have dominated American politics since Clinton. Trump has explicitly called out FDR's new deal coalition, the coalition emplaced by vaguely authoritarian means quite similar to those he is using, that was the underlying basis for politics for almost the past century. I don't care for Trump's vision much more than I care for Roosevelt's or Clinton's. But claiming that this is "unprecedented" only serves to point people away from the prior time in history when this happened, when we utterly failed to stop Roosevelt and remove his power. Perhaps learning from history is the better choice so this time we can do a better job of it.
This tradition goes back further than Roosevelt. In addition to being a notorious bigot and racist, Woodrow Wilson was open about the idea that the Constitution was outmoded and needed replacing so that a technocratic government could take its place.
You also have Roosevelt's first appointment to SCOTUS, a literal hood-wearing klansman and true-blue progressive. Broadly the progressive movement was also home to a high level of racism; more of the paternalistic variety than the hateful, but still led to e.g. forced sterilizations. Progressives today have abandoned that, but there was no such radical realignment for them.
So, Roosevelt worked to find the necessary votes to pack the court. His "Judicial Procedures Reform Bill" was not so different from any of the other "judicial reforms" we've condemned when other strongmen around the world used them to strengthen their power. Politicians from Roosevelt's bloc spewed vitriol at the justices who were simply trying to do their jobs. In Iowa, effigies of the six justices who had opposed any of Roosevelt's actions were found hanged by nooses. Once Roosevelt secured political support and signaled his willingness to push for packing the court, the justices backed down and began ruling in his favor, repeatedly. Where months before it had struck down a New York minimum wage law, a nearly-identical law in Washington was deemed perfectly constitutional. The National Labor Relations Act was fine and dandy. Coal mining was suddenly interstate commerce after all. In fact, the Commerce Clause now covered everything; one clothing factory in Virginia was enough commerce to quality. Later, the court would rule that a man growing wheat for his own consumption was sufficient "commerce" to warrant near-limitless federal rule-making. After all, it meant he bought less wheat from someone else, so clearly it was within the feds' purview. Wickard v. Filburn stands as precedent today. The justices on that court kept their seats but gave up their power.
Now, another populist has shown up. One who has a different vision for the nation than that laid out by the neoliberal technocrats who have dominated American politics since Clinton. Trump has explicitly called out FDR's new deal coalition, the coalition emplaced by vaguely authoritarian means quite similar to those he is using, that was the underlying basis for politics for almost the past century. I don't care for Trump's vision much more than I care for Roosevelt's or Clinton's. But claiming that this is "unprecedented" only serves to point people away from the prior time in history when this happened, when we utterly failed to stop Roosevelt and remove his power. Perhaps learning from history is the better choice so this time we can do a better job of it.