Constitutional revolution is going mainstream.

If the Republican Senate confirms a Trump appointee to fill Justice Ruth Bader Ginsburg’s Supreme Court seat right before or after the election, progressives say Democrats, if they sweep in November, should retaliate by packing the Supreme Court.

None of this comes out of the blue. The left is disenchanted with our country, and especially its governing institutions, which it believes are shot through with racism and deeply undemocratic. Democrats have gone from assuming a few years ago that they have a permanent majority to assuming that they can’t possibly win under such a rigged system.

They no longer want to live under a government that checks majoritarian passions, recognizes the importance of states in our federal system and features a Supreme Court that is supposed to render independent judgments based on the law and the Constitution. All of this, once a matter of basic civics, is now for suckers.

Before its new fashion, court-packing used to be notorious, the ill-considered move that President Franklin Roosevelt couldn’t see through even at the height of his power.

For good reason. To add a bunch of new seats to the Supreme Court explicitly so a Democratic president could fill them would radically diminish the Court’s standing. It would invite Republicans to counter with their own bout of court-packing when they again return to power. The Court would become merely a partisan plaything and essentially an adjunct to the legislative branch — all that would stay the same would be the black robes.

And for what? To compensate for a duly elected Republican Senate acting on its prerogatives to block one Supreme Court nominee (Obama nominee Merrick Garland) and potentially confirm another (Trump’s nominee to fill the RBG seat).

The Senate itself is now an affront because small states get equal representation with large states. Never mind that this arrangement was at the center of the deal that gave us the Constitution. Never mind that the Constitution stipulates that this provision is unamendable. Never mind that prior to 2014 the Democrats controlled the Senate and didn’t seem overly concerned about the body’s alleged lack of legitimacy.

It’s not a failing of our constitutional design that Democrats have made themselves so hateful to rural voters that they despair of reliably holding the Senate going forward. As a corrective, they are threatening to eliminate the filibuster to allow them to add Washington, D.C., and Puerto Rico as states to boost their number of senators, a maneuver that smacks of pre-Civil War era power politics.

All of this talk is an awkward fit for Joe Biden’s candidacy. We are told that Biden is an inoffensive institutionalist and committed moderate, but if Republicans defy his wishes on the RBG seat, he will respond by blessing outlandish changes to our system passed by narrow majorities.

And, by the way, Biden better win. Shadi Hamid of The Atlantic wrote a piece expressing his worry “that Trump will win reelection and Democrats and others on the left will be unwilling, even unable, to accept the result.” He raises the possibility of “mass unrest and political violence across American cities.”

Accepting the result of an election is a pretty important norm — unless you’ve convinced yourself you live under a hideously undemocratic regime with no legitimacy.

Rich Lowry is editor of the National Review.