In my previous post, I suggested there isn’t, but maybe I wasn’t being sufficiently imaginative. It is possible that a constitutional crisis would erupt if Trump fires Sessions, or forces Sessions to resign (p=0.9). But how, exactly? A political crisis, yes. Many die-hard Trump supporters appear to be die-harder Sessions supporters. Trump’s already low popularity could plunge, putting his agenda into even greater peril than it is already in. But nothing stops Trump from appointing a new attorney general, and then tweeting and playing golf until 2021.

I want to maintain the notion that a constitutional crisis takes place when the government can no longer operate or faces significant disruptions because of disagreements among key public officials about what the constitution requires; broader definitions just seem to be gestures at drama. What does seem possible is that the firing of Sessions would create a breach between Trump and Republican Senators, many of whom are strong Sessions supporters. They could retaliate by refusing to confirm a new attorney general, or other nominees, for good, or (more likely) unless Trump appoints to the position someone who has a reputation for independence. This would mean that the standoff between Trump and the Justice Department would continue for the foreseeable future.

The underlying constitutional norm at stake is the independence of the Justice Department. This might seem like an odd claim: isn’t the Justice Department in the executive branch, which the president heads? But it seems increasingly clear that a new constitutional norm has arisen, possibly traceable to Watergate, according to which the Justice Department is semi- or maybe completely autonomous, much like the judiciary. You might think of Trump as a kind of unlikely James I to Sessions’ even unlikelier Lord Coke, who resisted the king’s efforts to subordinate the judiciary to the executive, and helped establish the principle of judicial independence. But for Trump, the relevant norm is not judicial independence but prosecutorial independence. Trump is trying to reverse the norm, but it has many defenders in both parties.

There is logic to all this. The principle of judicial independence is entrenched; not even Trump can touch it. But our system has maneuvered around this principle by granting increasing power to prosecutors, which they can use to harass people with investigations and selective prosecutions based on general laws that are otherwise not enforced. This power has grown to such an extent that it can easily be abused by a powerful president if he were really to exercise control over prosecutors, as the traditional legal sources maintain he has. The norm of prosecutorial independence, if one can call it that, has evolved over the last forty years to cabin the president’s discretion and prevent this kind of abuse. Trump is the first president to challenge it.