Ariane de Vogue for CNN:

As emergency petitions concerning voting rights challenges have raced through the courts in the final weeks of the election, judges and justices have found themselves trying to explain a legal doctrine that was designed to preserve the integrity of the electoral process.

But for a doctrine aimed at clarity, it has, in the age of coronavirus, raised plenty of confusion on its own, and it could swing the presidential election. At issue: When should courts refrain from changing voting rules too close to an election in order to avoid causing voter confusion?

The so-called “Purcell Principle” arises out of a 2006 Supreme Court case concerning a strict voter-identification law. A federal appeals court blocked the law pending appeal. But the Supreme Court stepped in and allowed the law to take effect.

In doing so, the Supreme Court sent a strong message to federal courts: “Court orders affecting elections, especially conflicting orders, can themselves result in voter confusion and consequent incentive to remain away from the polls.”…

Election law expert and CNN contributor Rick Hasen has coined the term “Purcell Principle” and said it needs tweaking

.In a 2016 law review article, Hasen said the court was right in Purcell to “note special considerations in election cases,” because voters could be not only confused but also disenfranchised. They could, for example, show up without the right documentation or at the wrong polling place. But he said those interests should not be the sole consideration of a court.Hasen said courts should also consider factors such as the likelihood of success of the case on the merits, and the potential irreparable harm to both sides.

Early next week, Amy Coney Barrett is set to take the seat left vacant by Justice Ruth Bader Ginsburg’s death. Her view on Purcell might represent the deciding vote.