WASHINGTON -- Hours before Supreme Court Justice Anthony M. Kennedy announced his retirement, Justice Elena Kagan sketched out the court's potential dystopian future, with justices unencumbered by precedent and energized to make the law conform to their policy preferences.

Dissenting in the public-employee union-fees case, Kagan explained that the worst part was not that the five-justice majority was wrong -- it was that its ruling so cavalierly "subverts all known principles" about being reluctant to overturn prior cases.

In this instance, it was a 41-year-old decision known as Abood. In the future, well -- you can guess what other holdings the court's conservatives have on their hit list.

"The majority has overruled Abood for no exceptional or special reason, but because it never liked the decision," Kagan wrote. "It has overruled Abood because it wanted to. Because, that is, it wanted to pick the winning side in what should be -- and until now, has been -- an energetic policy debate."

You might read Kagan's dissent -- you might look at the ghastly landscape of this court term -- and shrug off Kennedy's departure. After all, he formed part of the majority whose disrespect for precedent Kagan eviscerated. After all, he joined with the conservative pack in every one of the ideologically split 5-4 cases decided this term.

Yet the court without Kennedy could become -- it is all but certain to become -- so much worse. Consider this: the swing vote of the foreseeable future is Chief Justice John G. Roberts Jr. On the court that Kennedy joined three decades ago, a justice like Roberts would have been positioned firmly on the rightward flank. On today's right-tilting court, the undeniably conservative Roberts passes for a middling squish, with Justices Clarence Thomas, Samuel Alito and Neil Gorsuch anchoring the right, with an unnamed ally to come.

So Kennedy's departure feels like a bad sequel to the circumstances of his arrival, when another swing justice whose position set the future of the high court on divisive issues such as abortion and affirmative action announced his retirement. Back then, the departure of Lewis F. Powell Jr., and President Ronald Reagan's initial selection of appeals court judge Robert H. Bork to replace him, unleashed a battle so fierce it became a verb.

From my vantage point -- and I covered the Bork confirmation -- it was a fight worth waging with all necessary ferocity. A Justice Bork would have been a disaster; his writings illustrated how intensely he disagreed with, and would be inclined to jettison, decades of precedent.

Bork's defeat produced, eventually, Kennedy, and with him, three decades of unpredictable, sometimes infuriating decision-making that nonetheless kept the court on a steady course. The right to abortion was restricted, but the fundamental protection remained in place. So, too, with affirmative action. Meantime, Kennedy steered the court, and the country, to a nobler place on the rights of gay and lesbian Americans.

Which is why, notwithstanding this final, disappointing term, his departure is so alarming. And why this must be another Bork moment -- insisting on a nominee that is, to invoke the language of the Bork debate, within the broad mainstream of judicial thought.

And one who, like swapping Kennedy for Powell, will not radically alter the balance of the court. A nominee should be considered on his or her merits, primarily, but it is politically naive and, I think, substantively mistaken not to take into account the impact of that nominee's views on the overall balance of the institution.

The court functions best -- it tends to produce better reasoned opinions, more acceptable to the public -- when it does not tilt too decidedly in either direction. If regular order had been followed, Justice Merrick Garland would be sitting on the court, occupying a centrist role; his shameful absence offers another argument for insisting that Kennedy's replacement display some of Kennedy's qualities of moderation.

Democrats can squeal and stall, but not much more. The real responsibility rests with those Senate Republicans who have styled themselves as independent of Trump. Susan Collins of Maine and Lisa Murkowski of Alaska, I'm talking to you. Retiring Sens. Bob Corker of Tennessee and Jeff Flake of Alaska, you especially. The Constitution assigns you a role. Play it. If this sounds fanciful, consider this piece of pre- tribal history: Six Republicans voted against Bork, two Democrats for him.

Insist on a justice who doesn't simply want to "pick the winning side," as Kagan said, but who will understand, among other things, that respecting precedent is a true conservative value.

(c) 2018, Washington Post Writers Group