When Sen. Susan Collins says her primary concern in evaluating President Trump’s next Supreme Court appointment is whether the nominee adequately respects precedent, that bar is so low as to be essentially meaningless. Every conceivable nominee will offer the same basic commitment to “stare decisis,” a legal doctrine that says previously decided points of law should be treated as settled. But such generic assurances tell us nothing useful about how the nominee will actually decide the cases that people care most about.

As a moderate Republican who supports abortion rights, Collins says she will not vote to confirm a nominee who “demonstrated hostility” to Roe v. Wade. But because she herself views Roe as settled law, she does not feel compelled to apply a litmus test and instead just wants to be sure that the nominee is committed to precedent as a general matter.

Citing conversations she had with Justice Neil Gorsuch about the importance of precedent, Collins predicted that even he would not vote to overturn Roe despite his conservative bona fides. This prediction provoked some skepticism among legal commentators, who pointed to the 11 instances, from just his first term on the court, in which he overruled or expressed a desire to revisit prior case law.

Gorsuch apparently convinced Collins of his deep respect for precedent by referring to a book he co-authored on the subject. I examined Gorsuch’s book, “The Law of Judicial Precedent,” while preparing a review essay for the Harvard Law Review. I offer here a couple of clarifications about what respect for precedent actually means.

First, all lawyers and judges understand that the doctrine of stare decisis is not absolute. The treatise acknowledges the uncontroversial point that precedent may be overruled and outlines the various circumstances in which it is appropriate to do so. Just last month, the court (in an opinion joined by Gorsuch) overturned a 40-year-old precedent in part because it was “poorly reasoned.” There is no basis for presuming that Roe is any safer merely because Gorsuch and the next nominee will both have professed a commitment to stare decisis.

Second, the import of past decisions can be substantially weakened even if they haven’t been formally overruled. Gorsuch’s treatise details how courts can distinguish a past decision or read it narrowly so that it has no force beyond its particular facts. Because later courts have significant discretion in deciding how to interpret and apply past decisions, they can plausibly claim to be respectful of precedent even as they work to undermine it.

Abortion-rights advocates are, therefore, as concerned about the scaling back of Roe as they are about its outright overruling. The court could easily render the right meaningless by upholding regulations that make abortions effectively impossible to get. Indeed, the court has recently been criticized for chipping away at other landmark decisions, like Miranda v. Arizona, by limiting the scope of the rights they established.

In short, Collins is wrong to suggest that those concerned about the future of abortion rights should take comfort in a nominee’s generic assurances about respect for precedent.

Of course, any nominee who gave a stronger endorsement of Roe would likely be ruled out by the president or the other Republican senators. So if Collins actually wants to prevent Roe from being overturned or undermined, her best option is not to seek or rely on commitments of any sort, but rather to insist on the appointment of an independent-minded jurist with a centrist record.

She has not yet made such a demand, preferring to default to her deferential approach of evaluating judicial nominees based on their intellectual qualifications and temperament rather than ideology. Collins deserves credit for applying the same standards to nominations from both Democratic and Republican presidents.

But here again Collins is wrong to invoke precedent – in this instance, her own past approach to judicial nominations – because the situation she faces is unprecedented.

Replacing the centrist Justice Anthony Kennedy with a far-right conservative will substantially alter the balance of the court. What’s more, this pending shift is possible only because Senate Majority Leader Mitch McConnell refused, over Collins’ objection, to hold hearings for President Obama’s nominee for the last Supreme Court opening.

A third distinguishing factor is that Collins holds significant leverage as one of perhaps two swing votes in a closely divided Senate. If she chooses to squander that leverage, that is her prerogative. But if the eventual nominee ends up disappointing her and her constituents, she should not be allowed to invoke precedent as an excuse when it was clear from the outset that she had the power and every reason to take a stronger stand.