This is somewhat misleading. The 9-Justice equilibrium has persisted in part because the Court has rarely been out of step with national majorities.
[brief thread] The version of the Warren Court with a liberal median vote lasted for all of 5 years, which was not coincidentally the 20th century peak of liberal policymaking in Congress. Calling it "countermajoritarian" is, at best, incomplete.
As Mark Graber says, a generation of scholars has discussed the Warren Court as if Barry Goldwater won a landslide in 1964.
And even if the GOP controlled Congress in Nixon's first term, they had no need to consider court-packing, because Nixon had restored a Republican majority on the Court before the end of his first term.
And note that the restoration of a GOP majority was facilitated in part by a too-little-discussed act of constitutional hardball: the Fortas filibuster, which ended up giving Nixon two quick nominees, ending not only the Warren Court but the liberal median vote.
The control of the Court by country-club Republicans since then has produced conservative courts that have produced enough high-profile liberal wins that both sides have found the outcomes tolerable -- but this is about to end papers.ssrn.com/sol3/papers.cf…
It's also important to understand that the 9-member equilibrium is a contingent outcome. Had the Court continued to attack the New Deal in 1937 some combination of court-packing and further jurisdiction-stripping would almost certainly have happened
To be clear, I agree 100% with @BrendanNyhan that, ceteris paribus, the 9-member equilibrium is preferable to escalating rounds of Article III measures by Congress to manipulate the courts
But an entrenched Republican majority Supreme Court refusing to allow Democratic Congresses and presidents to govern -- which is possible -- is not democratically defensible or sustainable either.
The advise and consent power is not a very good fit with elite ideological polarization, and this will have major consequences for judicial review. @imillhiser is right that we need to start considering the possibilities.
And if anyone still reading is interested in why we need to get beyond the "countermajortarian difficulty" framework for evaluating the democratic legitimacy of judicial review, @djw172 and I have a book for you! amazon.com/Judicial-Revie…
