Apparently there’s some question about the strategic imperative facing liberal Supreme Court Justices Stephen Breyer an Ruth Bader Ginsburg now that Democratic senators have fought back against Republican obstruction on nominations. Let me clear this up. There’s absolutely no question about it; if they want to secure the principles they have fought for during their careers, the best thing both of these senior liberal justices can do is to retire right now.

After all, the main lesson of this Senate showdown was not that Democrats would fight back; it’s that the current Republican Party stands strongly behind the idea of “nullification” — that even after losing presidential and Senate elections, Republicans will use whatever ability Senate procedure gives them to prevent President Obama and the Democratic Senate majority from fulfilling the normal governing practice of filling vacancies in the government, including the federal bench.

It is likely, then, that Ginsburg and Breyer will only be replaced by similar mainstream liberals if there is unified Democratic control of the White House and the Senate.

If Republicans happen to gain six or more Senate seats in 2014, and with them a Senate majority, it’s very likely they will simply bottle up most judicial nominations in committee, not even allowing floor votes. That would almost certainly apply to Supreme Court picks. Which Judiciary Committee Republicans would defy tea partiers and risk a strong primary challenge by voting to move a nominee to the Senate floor?

And if there’s anything that the D.C. Circuit Court battle has demonstrated, it’s that Republicans are perfectly willing to invent and then defend preposterous “principles” in order to gain partisan and ideological advantage in the courts. It’s hard to believe that anyone bought the idea that it was “court packing” for Obama to fill existing vacancies, or the ad hoc “workload” arguments that Sen. Chuck Grassley and other Republican senators used as justification for their filibusters. Surely they would invent some similar fig leaf for a blockade of any Supreme Court vacancies, and it wouldn’t matter at all to them that no one took it seriously.

That’s after the 2014 elections. In 2016, in addition to another shot at Senate control, Republicans certainly could win back the White House, thus insuring that any vacancies over the next four years would be filled by a solid, safe, conservative.

For Ginsburg and Breyer to risk their judicial legacy on predictions of the outcomes of these elections is nuts. It’s easy to predict what kind of judges a Republican president would select, but political scientists would tell the justices that there’s no way of predicting any presidential election two or more years in advance.

Yes, both Ginsburg and Breyer could have a dozen, or for all I know two dozen, productive years ahead of them. Yes, they both appear to still be at the top of their games right now. Yes, they would be giving up a lot personally if they stepped down.

But the strategic imperative is just as clear as it is harsh.  If they care about the principles they have worked for, it’s time to step down.