The impeachment trial included several arguments that should not be allowed to calcify into constitutional precedents. They should, instead, be treated like Lincoln treated Dred Scott: as pertaining to the immediate case but open to challenge in future ones. To wit:

Impeachment as Criminal Trial: Trump’s defenders argued that his behavior did not meet the criminal definition of incitement. But he was never charged with a criminal offense that threatened his liberty. He was, rather, impeached through a political process whose sole object—and whose framework of discussion—should have distilled to one question: Did it serve the public good for Trump to be convicted or acquitted and, concomitantly, to be eligible or ineligible to run for office again? Speaking of which:

Impeachment as a Threat to Due Process: The complaint that Trump was denied due process, or his First Amendment rights, was perhaps the most pernicious and misleading constitutional claim. That is not simply because both claims were false: Trump was not denied any process that was due to him, and the First Amendment has never protected incitement. The crucial point is that they were irrelevant. Trump’s rights were not the issue. For that matter, neither was Trump himself. 

The Constitution describes public office as a “trust,” a legal term of art that refers to property controlled for the benefit of another. An impeached president is in a situation similar to the executor of a trust who is accused in a civil proceeding of misappropriating funds. He or she may or may not be guilty, and his or her fitness for the role is reasonably open to dispute. But the trustee has no personal right to control benefits intended for others. The legal concept indicates the opposite: The proper lens is the rights of the beneficiaries.

Impeachment as a Slippery Slope: Trump’s defenders inquired whether former Secretary of State Hillary Clinton could still be impeached for actions while she occupied that office. Their argument was the slippery slope: If this, why not that, and that, and so on? That abrogates the imperative of prudential judgment. It is as much as to say: This could be done so I fear I will do it. 

Granting for the sake of argument that Hillary Clinton could still be impeached, that does not excuse members of Congress from judging whether she should be, nor is it pertinent to the question of Donald Trump’s guilt or innocence. Similarly, legislators are capable, or should find other work if they are not, of differentiating whatever Clinton is supposed to have done as secretary of state from a president of the United States inciting an insurrection against Congress. Both may be impeachable. One is objectively graver than the other. Robert Bork wrote of judges that they “live on the slippery slope of analogies; they are not supposed to ski it to the bottom.” The perils of slippery slopes are worth contemplating before skiing them. But that is not a reason never to embark. Prudence distinguishes between navigating slippery slopes carefully and assuming the peaks and bottoms of them are identical.

One hopes, of course, that arguments like these will not have an opportunity to harden into precedent because impeachment is a device rarely used. But it should not be vitiated either. The problem with impeachment is that it has become unthinkable and consequently serves little use as a deterrent. The second Trump acquittal did not help. It was not the acquittal itself that weakened impeachment. It was the arguments made to get him off the hook. Whether we accept or reject those arguments is still within our control.