U.S. politics was fractured and its system of government under stress even before Justice Anthony Kennedy said on Wednesday that he'd retire from the U.S. Supreme Court at the end of July. The announcement promises new extremes of partisan rancor, in Washington and beyond, as President Donald Trump and the Republican Senate majority move to install a conservative replacement and shape the character of the highest court for years to come.

Elections have consequences, as somebody once said. Trump and the Republican majority are within their rights to nominate and confirm a justice whose legal philosophy comports with theirs. But they should nonetheless be mindful of how much is at stake.

To discharge its vital functions, the Supreme Court must retain respect, however grudging, across the broadest spectrum of public opinion. An appointment that makes this impossible would be the height of irresponsibility. Already compromised in this regard, and widely seen as predictably divided along partisan lines, the court needs a successor to Kennedy who will be what he was: An exception; an unpredictable moderate; leaning conservative, yet willing to disappoint each party in turn, as his legal reasoning dictated.

Democrats, citing precedent, say the appointment ought to wait until after the midterm elections. GOP leader Mitch McConnell blocked consideration of Merrick Garland, President Barack Obama's nominee for the court, for nearly a year ahead of the 2016 elections, arguing that such a momentous appointment should await a fresh political mandate. Wrong as that was, consistency would demand a similar delay now — but the Democrats lack the votes to insist on it. The Republicans can get their way in 2018 by moving promptly, and they surely will.

Even so, moderate Republicans — whose votes will be needed to confirm the appointment — can and should impose restraint on the president and the Senate's conservative hard-liners. They should insist on a nominee who's capable of independent thought, and preferably one whose name is not on the list of certified conservatives whom Trump says he favors.

It would be pointless, no doubt, to ask such restraint of President Donald Trump himself. He sees an opportunity for another "win," and one may be sure he'll seize it if allowed to. But those Senate Republicans who are alarmed by this administration now have an opportunity to intervene at a truly crucial moment, and check the long-lasting harm Trump might do by nominating a reliably and reflexively illiberal justice.

Nothing matters more at this juncture in U.S. history than maintaining respect for the Supreme Court. If Senate Republicans fail to do that, it will be their most egregious failure to date.

FROM AN EDITORIAL ON BLOOMBERG VIEW