Democrats had harsh words for the president during Robert Mueller’s appearance before the House Judiciary and Intelligence committees on July 24. “Any other person who acted in this way would have been charged with crimes,” said Judiciary Committee Chairman Jerry Nadler, “and in this nation, not even the president is above the law.” Intelligence Committee Chairman Adam Schiff accused Donald Trump of “disloyalty to country,” what he termed a violation of “the very oath of citizenship.” Chair of the House Democratic Caucus Hakeem Jeffries walked Mueller through the components of an obstruction of justice offense before declaring, “The president must be held accountable one way or the other.” And after the close of the hearings, Speaker of the House Nancy Pelosi announced, “These charges [of obstruction of justice], as have been demonstrated today, are indictable offenses had they been committed by anyone else.”

These four members of Congress all number among the leadership of the House Democrats, but they have something else in common: None of them supports the formal opening of an impeachment inquiry, much less articles of impeachment.

The situation has become a little muddled in recent days as the House Judiciary Committee announced following Mueller’s testimony that it was beginning an “investigation to see if [it] should recommend articles of impeachment,” which Nadler distinguished, somewhat opaquely, from an impeachment inquiry. Nevertheless, Nadler made clear that he was not making a guarantee that articles of impeachment would emerge from the process. And other members of the Democratic leadership are holding the line: An impeachment inquiry, Pelosi argued at the post-hearing press conference, must be “done with our strongest possible hand, and we still have some outstanding matters in court.” Schiff later tied this to a more prudential argument, which Pelosi herself has made in the past: Impeachment proceedings will not succeed in removing the president from office, he said, and therefore the House should refrain. The gist of this position seems to be that the president’s actions are abhorrent—indeed, the caucus seems to have settled on the belief that they are likely criminal—but that this does not require the House to take formal steps toward impeachment. However disloyal and criminal the president may be, the argument goes, impeachment remains a matter of the House’s discretion.

After the last burst of impeachment talk from the Democrats, I argued here on Lawfare that this case is incoherent. There is no way to sever entirely the political judgment of whether or not to initiate proceedings from the moral and constitutional judgment of whether “high Crimes and Misdemeanors” have taken place. A speaker of the House faced with a sufficiently egregious action by the president would feel some obligation to begin an inquiry—and that means that, for all their words, Nancy Pelosi and other members of the Democratic leadership have made the judgment that Donald Trump’s behavior does not cross that line.

There is an intuitive response to this argument, as Marty Lederman pointed out: Perhaps the Constitution simply imposes no obligation to impeach, even under the most extreme of circumstances. Schiff made this argument following Mueller’s testimony, reasoning that Trump “has committed offenses against the law that would certainly qualify as impeachable offenses…. The Constitution makes clear, though, that Congress isn’t compelled to do an impeachment even when we know there are impeachable offenses.” And Nadler said that “the president richly deserves impeachment” but that the Judiciary Committee needs to gather more information before moving forward with articles to that effect.

In this view, impeachment is an option, never a command. It is, after all, a political process, assigned by the Constitution to the branch of government that is by design most responsive to political considerations—and seldom fettered by principle. With this in mind, is it really right to boil down the question of impeachment proceedings to a matter of moral duty, rather than a pragmatic political judgment? There’s a strong textual basis for this argument: The Constitution grants to the House “the sole Power of Impeachment” and to the Senate “the sole Power to try all Impeachments,” but it includes no language requiring either chamber to take up that power in particular circumstances.

From where in the Constitution, then, would an obligation to begin an impeachment inquiry flow?

I have an answer: the legislators’ oath.

The Constitution states that members of Congress—along with every state legislative official and every judicial and executive official of both the state and federal governments—“shall be bound by Oath or Affirmation, to support this Constitution.” (The sole exception is the president, whose oath the Constitution deals with separately.) The text has taken several forms, but currently members of Congress swear as follows:

I do solemnly swear (or affirm) that I will support and defend the Constitution of the United States against all enemies, foreign and domestic; that I will bear true faith and allegiance to the same; that I take this obligation freely, without any mental reservation or purpose of evasion; and that I will well and faithfully discharge the duties of the office on which I am about to enter: So help me God.

My contention is that this promise to “support and defend the Constitution” and to “well and faithfully discharge the duties of the office” imposes—at some point and under sufficiently dire circumstances—an obligation to take action against a president who has abused his office.

To be clear, I do not want to argue that the oath imposes any kind of justiciable obligation on members of Congress. Writing about the presidential oath in the first weeks of the Trump administration, Benjamin Wittes and I argued both that the oath was the underpinning of a great number of assumptions foundational to the constitutional structure and that the question of presidential compliance with it was “the very definition of a political question.” The same is true here. Though the courts haven’t explicitly ruled on the matter of the oath as a political question, they have hinted at an unwillingness to dig too deep into the issue: In a 1970 case regarding a state loyalty oath, Justice Marshall Harlan exclaimed, “I consider it most unfortunate that our past decisions in this field can be construed even to require solemn convocation of three federal judges to deal with a matter of such practical inconsequence.” And moving beyond the courts, oaths might even be beyond the capacity of other members of the legislature to judge: In Bond v. Floyd, the Supreme Court held that a majority of state legislators may not pass judgment on the sincerity with which another of their number swore the oath of office. The judgment of whether the obligation set by the oath has been met is between a member of Congress and his or her own conscience, and it is up to the public to adjudicate in elections.

But consider the following example: The Senate has the responsibility to provide “advice and consent” to the president’s appointment of public officials. After the death of Justice Antonin Scalia in 2016, Senate Majority Leader Mitch McConnell blocked President Obama’s nomination of Judge Merrick Garland, holding open the seat that would eventually be filled by Neil Gorsuch. The months after Scalia’s death were filled with debate over whether or not the Senate had, as Obama and Democratic senators argued, some constitutional “duty” to vote on Garland’s nomination. Interestingly, proponents of a vote regularly pointed to senators’ oaths: “The senators swore their oath to the Constitution,” Martha Minow and Deanell Tacha argued in the Boston Globe. “If Senate Republicans refuse to consider the president’s nominee, they will be willingly violating the spirit of that sworn oath,” warned Sen. Chris Murphy. His Democratic colleagues Sens. Cory Booker, Tom Carper and Jeanne Shaheen, among others, similarly cited the oath in their comments on Garland.

The argument that the Senate behaved unconstitutionally in refusing to consider Garland’s nomination is, at the very least, contentious; as critics pointed out, there is nothing in the text of the Constitution that obviously mandates action on the Senate’s behalf. But that’s precisely the point. The act of considering a judicial nomination is discretionary in precisely the same way as is the act of considering an impeachment. And in the same fashion, to wholly refuse to engage it raises questions about whether one is abandoning one’s job. As Justice Joseph Story wrote of the Article VI oath requirement in his treatise, “Commentaries on the Constitution,” oaths “have a solemn obligation upon the minds of all reflecting men”: The oath requirement stems from “the plain right of society to require some guaranty from every officer, that he will be conscientious in the discharge of his duty.”

The common framing of the Garland episode as a derogation of the legislative oath was rooted in the intuition that in blocking Garland’s nomination until the election of a president of the Senate majority’s own party, the Republican caucus was not honoring its promise to “support and defend the Constitution” and “well and faithfully” carry out the duties of the senatorial office. It was an allegation that McConnell was not acting “conscientious[ly] in the discharge of his duty,” to use Story’s words—a duty to, as Story describes it, “the welfare and safety of the whole community[.]”

To bring out the point more vividly, let’s make the example more extreme. What if Hillary Clinton had won the 2016 election and a Republican-controlled Senate refused to move forward any judicial nominations made by her during her entire time in office—that is, not voting them down but refusing to allow a vote at all? Would this be consistent with the oath? (Republican Sen. David Perdue thought not, telling the AP the day before the election that such an approach would amount to a “dereliction of duty”: “I’m going to be one that says ‘Look, our oath of office says that we’re going to govern, and that’s what we should do.’”) What if both Republicans and Democrats categorically decided that they would not move forward on any nominations made by a president of the opposite party while their party controlled the Senate? Does this behavior fit the definition of “support[ing] and defend[ing] the Constitution”?

Or consider a different example. What if, the next time the Trump administration reaches an impasse with Congress over spending and the government shuts down, the speaker of the House refuses to negotiate at all and decides not to fund any portion of the federal government? The Trump administration and the Democratic majority in the House of Representatives have now reached a deal to avert a possible breach of the debt ceiling in September or October—but imagine if the Democrats had refused to come to the table. What if Pelosi had simply walked away and decided that she would let the U.S. default on its debt rather than sit down with the president? What if she stuck to this position even as the country drifted toward financial collapse? These, too, like the impeachment power, are matters of pure discretion, powers granted to the legislature but whose use is never mandatory. The power of the purse, after all, is not a requirement to spend. Yet would such conduct pass Justice Story’s test?

I would argue that the answer is no—that the oath imposes some basic level of constitutional responsibility in certain circumstances. One can amuse oneself by coming up with even more bizarre hypotheticals that would violate the oath. (What if Congress decided to consider only nominees submitted by the president on days when it happened to be raining? What if Congress stripped all funding from the Justice Department because all 535 members decided they found the attorney general’s habit of playing bagpipes objectionable?) But here I’m concerned primarily with situations in which Congress fails to take action in circumstances that seem to demand it, rather than situations in which Congress takes needlessly absurd action.

In examining the substantive obligations imposed by the oath, “Commentaries on the Constitution” is not a bad place to start—but it is far from the only source to consider. Writing about the presidential oath, Wittes and I argued that it is “a fundamental underpinning not only of many of our cultural assumptions regarding presidential behavior, but also of the judiciary’s willingness to grant deference to the executive branch, particularly in the realm of national security”—and that, when the president acts in a manner that causes other government actors and members of the public to doubt his oath, aspects of the constitutional system begin to shift. While this second aspect of our argument focused solely on the president, we noted that the role of the oath in “inter-branch deference and comity” stretches beyond the executive: “When the courts presume a statute constitutional, they do so because it was passed by a coordinate branch of government whose members swore oaths to protect the Constitution.”

In Knox v. Lee, Justice William Strong, writing for the court in 1870, stated this idea clearly: “A decent respect for a co-ordinate branch of the government demands that the judiciary should presume, until the contrary is clearly shown, that there has been no transgression of power by Congress—all the members of which act under the obligation of an oath of fidelity to the Constitution.” And a century later, in Cole v. Richardson, Chief Justice William Rehnquist wrote that the oath reflects an assurance “that those in a position of public trust [are] willing to commit themselves to live by the constitutional processes of our system.”

More recently, in Boumediene v. Bush, both Justice Anthony Kennedy, writing for the majority, and Chief Justice John Roberts, in dissent, pointed to the congressional oath. “The usual presumption is that Members of Congress, in accord with their oath of office, considered the constitutional issue and determined the amended statute to be a lawful one,” said Kennedy, reading Congress’s action as queueing up the matter of constitutionality to be considered by the Supreme Court as a coordinate branch. Roberts countered that the Supreme Court had jumped too quickly to the constitutional question of habeas instead of requiring that the Guantanamo detainees first exhaust their statutory rights under the Military Commissions Act, writing that “[r]espect for the judgments of Congress—whose Members take the same oath we do to uphold the Constitution—requires no less.” The chief justice’s point is a reminder that the courts look to the congressional oath not only as the foundation of the presumption of constitutionality but also as the foundation of the constitutional avoidance canon. Congress has made its independent judgment on the constitutionality of a statute in passing it; the courts should not disturb that judgment unless absolutely necessary. And it is because of their trust in the oath of members of Congress that the courts then assume some degree of good faith in the constitutional judgments of Congress.

While the oath is an individual commitment, the presumption of good faith applies to the institution of Congress as a whole. This gets to a crucial difference between the congressional oath and the oath sworn by the president. Other members of the executive branch swear an oath as well, but ultimately it is the president who is responsible. As Alexander Hamilton wrote of the presidency in Federalist No. 70, dividing leadership among a group of people “tends to conceal faults and destroy responsibility”—and so it is with Congress. If one or both chambers of the legislature take an action that arguably defiles the oath, it is easier for any given member to minimize his or her own responsibility in that breach.

This is not to say that the oath asks less of members of Congress, only that they may find it easier to keep out of mind. Writing about his own oath in 2001, Rep. Vic Snyder acknowledged, “A presidential oath that is as important an influence over presidential behavior as the threat of election defeat or impeachment … and a judicial oath that in Marbury v. Madison shaped the power of the federal judiciary are tough competition for the legislative branch mass oath of 435 House members in a rowdy chamber.” But, Snyder argued, the congressional oath is still worth taking seriously: “[O]nly the most hardened cynic” could ignore its power.

With this in mind, now consider the matter of impeachment. In his 1974 book, “Impeachment: A Handbook,” Charles Black writes:

… Congress … rests under the very heavy responsibility of determining finally some of the weightiest of constitutional questions, as well as a great many important and difficult questions of procedure.… We ought to understand, as most senators and congressmen understand, that Congress’s responsibility to preserve the forms and the precepts of the Constitution is greater, rather than less, when the judicial forum is unavailable, as it sometimes must be.

The process of impeachment, in other words, is an act of constitutional interpretation by Congress. When Black writes of “Congress’s responsibility to preserve the forms and the precepts of the Constitution,” he echoes the oath’s obligation to “support and defend.”

So let us weigh another hypothetical. There is debate over whether firing the FBI director, in part because the director refused to drop an investigation to which the president objected, constitutes an impeachable or even a criminal offense. But what if, for example, the president targeted the FBI director’s house with a drone strike instead of simply firing him? This obviously fulfills the requirements for “high Crimes and Misdemeanors” for which the president may be impeached. It would also be so vile and indefensible—as Black puts it, “so seriously threaten[ing to] the order of political society as to make pestilent and dangerous the continuance in power of [the] perpetrator”—that the oaths of members of Congress would mandate the beginning of the impeachment process. If this came to pass and the House of Representatives stoically continued its budget negotiations with the White House, I don’t think anyone would argue that they were plausibly “support[ing] and defend[ing] the Constitution.” Nobody would argue that the House was being “conscientious in the discharge of [its] duty” under such circumstances, if the speaker decided to hold off on impeachment proceedings lest they boost the president’s popularity. I don’t think Adam Schiff would make the case that impeachment was merited but not mandated.

If I am correct on this point, then impeachable offenses have to be evaluated along a spectrum—from offenses that are impeachable but allow for some level of discretion on the part of Congress to offenses that are so extreme that members of Congress must either begin impeachment proceedings or breach their own oaths of office. This is what remains for members of Congress to decide: whether Donald Trump’s behavior, as described in the Mueller report and publicly displayed over the past two and a half years, is bad enough to cross this line.

So far, the view of the Democratic leadership seems to be that the line has not been crossed. Schiff and House Oversight Chairman Elijah Cummings indicated to CNN that they would support impeachment proceedings if the president refused to abide by a court order—suggesting that this, rather than the disloyalty and criminality of which Democratic leadership accused Trump, is the real line that has yet to be crossed. “Whatever decision we make [on impeachment] will have to be done with our strongest possible hand, and we still have some outstanding matters in court,” Pelosi said during a press conference following the Mueller hearings. At another point, she said, “This is about the oath we take to protect and defend the Constitution.”

The line between an impeachable offense and an offense that demands impeachment proceedings is not an obvious one. As with pain, everyone has a different threshold. It would not be an unreasonable assessment to make that Donald Trump’s actions as described in the Mueller report, considered alongside his other behavior over the past two and a half years, have breached that threshold. But the question of these legislators’ fealty to their oaths is up to them to judge.