When then-Sen. Barack Obama filibustered Justice Samuel Alito’s nomination to the Supreme Court, he was breaking an informal “rule” that said barring some extraordinary circumstance, a U.S. senator should vote for a nominee who was competent and qualified. The same could be said for then-Senate Majority Leader Harry Reid, who triggered the nuclear option, ending the filibuster for most presidential nominations.

And, of course, after the death of Justice Antonin Scalia, it wasn’t exactly benevolent of Mitch McConnell to refuse to consider any Obama Supreme Court nominee before the 2016 presidential election (although, just as Obama’s decision to filibuster Alito probably helped his career, McConnell’s maneuver was most certainly a shrewd political move).

Democrats understandably feel cheated and aggrieved. It is one thing not to have Merrick Garland seated, but it’s another to win the popular vote and then watch two conservative Supreme Court justices be put on the Court. If the roles were reversed, I sincerely doubt that McConnell and others would be saying, “Well, it’s all about power. and they are playing the game to the best that they are able.'”

When the ends always justify the means, then the means become more and more egregious in the service of the ends. The most common retort when this is pointed out is: well, what about Robert Bork? And that’s all well and good. Maybe Democrats should rethink the way they handled that nomination.

“ Nevertheless, replacing Justice Kennedy will come with a cost. Things are about to get even uglier. ”

And maybe Harry Reid should rethink why he did away with the filibuster. But at some point, this game of one-upmanship, turned mutually assured destruction, becomes unsustainable. “You’ll regret this, and you may regret this a lot sooner than you think,” then-Minority Leader Mitch McConnell warned when Reid went nuclear. Well, that works both ways.

What (aside from a desire to put country ahead of party) is stopping the next Democratic president with a Democratic Senate majority—say, Elizabeth Warren—from simply packing the Supreme Court? There’s nothing written in stone that says there has to be nine Supreme Court justices any more than there is anything saying you need 60 votes to confirm a judge, or that the Senate should have to vote on—or even consider—a president’s high court nominee.

Granted, after Franklin Roosevelt tried to pack the court in 1937, the blowback served to chasten future presidents. But so many of our World War II assumptions have recently been questioned with impunity. Why not this one? This is something that all Americans, but especially conservatives, should worry about.

In their terrific book Why Democracies Die, Harvard professors Steven Levitsky and Daniel Ziblatt talk a lot about something called “forbearance” (which, depending on your translation, is one of the “fruits of the Spirit”) that is necessary for the survival of liberal democracy. “What it takes for those institutions to work properly,” Levitsky told NPR back in January, “is restraint on the part of politicians. Politicians have to underutilize their power. And most of our politicians, most of our leaders have done exactly that. That's not written down in the Constitution.”

But in today’s world, that’s all out the window. As Miguel Estrada and Benjamin Wittes observe in The Washington Post, “The only rule that governs the confirmation process is the law of the jungle: There are no rules. There is no point in pretending otherwise, as much as many of us wish it were not so.”

Now, I am not suggesting that Donald Trump should wait until after the midterms to nominate a replacement—or that he should nominate a moderate or a liberal. Quite the contrary, I’m remarking on the fact that we have arrived at a point where—because of the high stakes and past transgressions—the normal and appropriate exercise of power is still seen by half of the country as an outrage.

Think of it. There’s nothing wrong with Justice Kennedy deciding to retire, and there’s nothing wrong with President Trump nominating a conservative to replace him. Really, on the merits, this development shouldn’t be generating so much angst. As Philip Bump notes, whoever replaces Kennedy—almost certainly a staunch conservative—would have voted the same way Kennedy did this term on the vast majority of cases.

Nevertheless, replacing Justice Kennedy will come with a cost. Things are about to get even uglier. The understandable reaction of Democrats will be to seek vengeance. This is a vicious cycle, and there’s no telling where (or if) it will end.

The presidency of Donald Trump has tested our institutions, but when it comes to how we treat Supreme Court nominations, these norms were eroding long before Trump descended that escalator. Both sides want to win this race to the bottom.