The job of the justices is to interpret the Constitution, not maintain a public image. The law profs who authored this are surely aware of that. "Illegitimate" means more than "people dislike it." I think the late Justice Scalia did things right: delivering decisions that aligned with his Constitutional philosophy, even if he ultimately found the results distasteful (nevermind what the public had to say!).

A small YouTube channel I found, hosted by a constitutional litigator, has a number of solid videos about the S.C., and about this "partisanship problem" in particular [1]. The D/R split of the S.C. is much fuzzier than I once thought.

[1]: https://youtu.be/WKfF-WhIm5o

The Supreme Court cannot be replaced without replacing the Constitution. This only shows that there are also many other reasons to replace the Constitution. But the level of stress that would be needed to trigger that process would make it impossible.

The comments section in that article is quite active.

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