Earlier this month, the effort to impeach President Trump looked like a #Resistance fantasy. The release of the Mueller Report seems to have shifted the debate dramatically. This week, Democratic presidential contenders Sen. Kamala Harris and Sen. Elizabeth Warren called on the House to impeach Trump for obstruction of justice. 

Is obstruction of justice an impeachable offense? Yes. It’s one of the few offenses where we have presidential precedent. Obstruction charges played a central role in two of the three serious presidential impeachment cases in American history, forming the basis for Article I of the charges against Richard Nixon, and Article II against Bill Clinton.

Should President Trump be impeached for obstruction of justice? I’m not going to answer that question here; like the cagey Mayor Pete, I’m “going to leave it to the House and Senate to figure that out.” Instead, I want to stress something that should be obvious, but tends to get lost amid the statutory exegesis in Mueller Vol. II: whether the president is guilty of criminal obstruction and whether he’s guilty of impeachable obstruction are different questions.

Summing up Article I of the case against Nixon, the 1974 House Judiciary Committee report explained that:

President Nixon’s actions…. were contrary to his trust as President and unmindful of the solemn duties of his high office. It was this serious violation of Richard M. Nixon’s constitutional obligations as president, and not the fact that violations of Federal criminal statutes occurred, that lies at the heart of Article I [emphasis added].

The Judiciary Committee report on the Clinton impeachment echoed that analysis a quarter-century later: “the actions of President Clinton do not have to rise to the level of violating the federal statute regarding obstruction of justice in order to justify impeachment.”

The standards are different because impeachment and the criminal law serve distinct ends and have very different consequences. “The purpose of impeachment is not personal punishment,” the Judiciary Committee emphasized in its 1974 staff report on “Constitutional Grounds for Presidential Impeachment”; instead, impeachment’s function “is primarily to maintain constitutional government.” And where the criminal law deprives the convicted party of liberty, a successful impeachment mainly puts him out of a job.

I’ve complained before about “the overcriminalization of impeachment,” the widespread tendency to confuse impeachment with a criminal process. Congress has contributed to that confusion by offloading much of its responsibility for policing executive misconduct to special prosecutors. Mueller wasn’t tasked with looking into “high Crimes and Misdemeanors”; his brief was to probe “federal crimes committed in the course of, and with intent to interfere with, the Special Counsel’s investigation.” Naturally, then, the report speaks in the language of the criminal law.

But impeachment aims at fundamental breaches of the public trust, and therefore, as Alexander Hamilton put it, “can never be tied down by such strict rules” as operate in the criminal law. In an impeachment proceeding, the key question isn’t whether the president technically violated one or more of the federal obstruction statutes. It’s whether his transgressions are serious enough to justify removal from office.

That sort of inquiry is, in many ways, less forgiving than the criminal law approach. Though the Constitution nowhere specifies a particular burden of proof for impeachment, “criminal prosecutions require that the government prove guilt beyond a reasonable doubt in a proceeding in which the defendant enjoys many significant procedural protections.” As Michael Rappaport has observed, “a criminal prosecution model underenforces against executive misconduct, because it ignores noncriminal misconduct that may justify dismissing an executive official,” such as “‘high Crimes and Misdemeanors,’ which need not constitute violations of criminal or civil law.”

A prosecutor needs to prove every element of a statutory offense: a generalized showing of contempt for the rule of law won’t suffice. It’s fair game in impeachment, however. “Unlike a criminal case,” the Nixon Inquiry Report explains, “the cause for the removal of a President may be based on his entire course of conduct in office. In particular situations, it may be a course of conduct more than individual acts that has a tendency to subvert constitutional government.” 

In other important respects, however, an impeachment inquiry can be more lenient toward the accused. “Not all presidential misconduct is sufficient to constitute grounds for impeachment,” the Nixon Inquiry Report emphasizes: “There is a further requirement—substantiality.” Impeachment should “be predicated only upon conduct seriously incompatible with either the constitutional form and principles of our government or the proper performance of constitutional duties of the presidential office.” Even provable, criminal obstruction will not meet the standard of “high Crimes and Misdemeanors” in every case.

For instance, when viewed through the lens of the criminal law, the case against Bill Clinton was quite strong. Here’s Judge Richard Posner’s assessment, from his 1999 book on the Clinton impeachment, An Affair of State:

To summarize, it is clear beyond a reasonable doubt, on the basis of the public record as it exists today, that President Clinton obstructed justice, in violation of federal criminal law, by (1) perjuring himself repeatedly in his deposition in the Paula Jones case, in his testimony before the grand jury, and in his responses to the questions put to him by the House Judiciary Committee; (2) tampering with witness Lewinsky by encouraging her to file a false affidavit in lieu of having to be deposed, … and (3) suborning perjury by suggesting to Lewinsky that she include in her affidavit a false explanation for the reason that she had been transferred from the White House to the Pentagon.

After the Senate trial, however, multiple senators explained their votes to acquit in terms of substantiality: that although obstruction could, under certain circumstances, merit removal, the offense in this case wasn’t grave enough to justify that penalty. There’s no “it was about sex” defense to a charge of criminal obstruction, but in an impeachment trial, what—if anything—the president was trying to cover up matters.

In Trump’s case, the Mueller Report outlines a (lackluster and inept) cover-up without an underlying crime. As the Report reminds us, “proof of such a crime is not an element of an obstruction offense”—for the purposes of a criminal conviction, it doesn’t matter whether there’s an underlying crime. But for the purposes of an impeachment, arguably, it should.

On the other hand, what’s in the Mueller Report is only part of the picture. As a group of prominent conservative attorneys and academics put it in a public statement released Tuesday:

The report’s details add to an existing body of information already in the public domain documenting the President’s violations of his oath, including but not limited to his denigration of the free press, verbal attacks on members of the judiciary, encouragement of law enforcement officers to violate the law, and incessant lying to the American people. We believe the framers of the Constitution would have viewed the totality of this conduct as evidence of high crimes and misdemeanors.

An inquest based on the president’s “entire course of conduct in office” could be a lot less forgiving.