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Amid the grandstanding in the House of Representatives, one key point can sometimes get lost: While impeachment is certainly a political process, it is not a purely political one. The judgments that Congress makes throughout the process are substantially but not entirely constrained by legal standards set out in the Constitution.

If impeachment were a purely political process, Congress could legitimately impeach and remove a president from office for any reason or no reason at all. This would make impeachment akin to a vote of no confidence in a parliamentary system, where the legislature can at any time remove its chosen prime minister—albeit with a heightened requirement for removal in the Senate. Conversely, if impeachment were a purely legal process, Congress’s sole function would be to determine the facts and apply the relevant legal standards to those facts to determine whether the president has committed an impeachable offense.

One way to understand how law and politics intersect throughout the impeachment process, therefore, is with this test: Imagine that a particular member of the House or the Senate believes that there is a “correct” legal answer to the question of whether, on the evidence before Congress, the president has committed an impeachable offense. Can they properly vote the other way? Can they vote, in other words, against the evidence? By applying this test to the different stages of the impeachment process, one can see which aspects of the decision to impeach a president are political in nature and which are legal.

Before examining each of the different scenarios, let’s consider the constitutional arguments on each side of the question. Even beyond the supermajority threshold for removal, the Constitution rather clearly rejects the view that impeachment is just a political vote of no confidence. The text consistently describes impeachment using legalistic language, empowering the Senate to “try” “Cases of Impeachment” and render a “Judgment” of “Conviction.” And the Framers famously rejected a proposal allowing the president’s removal for mere “maladministration,” substituting the more legalistic phrase high Crimes and Misdemeanors. The message is clear: Impeachment is an adjudicative process to determine whether the president has committed a certain kind of offense.

However, impeachment is clearly unlike other purely legal proceedings. Most significantly, it is conducted by Congress, a quintessentially political body. Grand and petit juries, which play analogous roles to the House and the Senate in ordinary criminal trials, are made up of private citizens who are not accountable to public opinion. An early draft of the Constitution placed the trial of impeachment in the Supreme Court. Most scholars today agree that impeachment cases cannot even be appealed to the Article III courts; the Senate’s judgment is absolutely final. It is not to be presumed that the Constitution would have committed impeachment to elected branches if the Framers had wanted the process uncontaminated by politics.

And although high Crimes and Misdemeanors seems to rule out a purely political process, it does not make evaluating whether presidential conduct warrants impeachment straightforward. Scholars generally agree that high Crimes and Misdemeanors does not simply mean ordinary criminal violations. Instead, it is at least largely concerned with abuse of power. And determining whether someone has abused their authority is not a straightforward legal judgment like whether a defendant has committed each element of a statutory crime. Nor is there a clear standard for which abuses of power are so grave that they require removal from office. As Alexander Hamilton noted in “Federalist No. 65,” impeachment “can never be tied down by such strict rules” as those in ordinary criminal trials. Even answering the legal questions of impeachment requires what he called an “awful discretion.”

With these general considerations in mind, let us consider whether a member of Congress may properly vote against the evidence in each of the four possible scenarios.

May the House impeach against the evidence? No, it may not. Gerald Ford famously remarked that an impeachable offense is “whatever a majority of the House of Representatives considers it to be at a given moment in history,” but this cannot be right. If the House could impeach for any reason or no reason at all, impeachment would become the kind of no-confidence vote that the Founders expressly rejected. If the House votes to impeach on any basis other than a considered legal judgment that the evidence shows that the president has committed a high crime or misdemeanor, as it best understands that term, it has abused its own authority. Arguably, voting for such an impeachment would be a violation of each member’s own oath of office.

May the Senate convict against the evidence? Similarly, the answer here is also no. If anything, this answer is even clearer than with the House. Senators swear an oath for impeachment trials to “do impartial justice according to the Constitution and laws.” If a senator concludes that the president’s conduct, as shown by the evidence at trial, does not amount to an impeachable offense, they are honor-bound to vote for acquittal. Again, conviction on any other basis would render meaningless the Constitution’s specification that officials shall be removed only upon conviction of a high crime or misdemeanor.

The power of impeachment and removal is limited and enumerated, like the rest of Congress’s powers, and if either the House or the Senate transgresses those constitutional limits, it has violated the law. True, there is no remedy for that violation, but that is all the more reason why Congress itself must take seriously the constraints on impeachment, and act against the president only on the basis of a sincere, considered legal judgment.

May the House decline to impeach against the evidence? This is where things get interesting. Can one imagine a situation in which the House should not impeach the president, even with a clear legal basis to do so? I think so. Suppose, for example, that during a time of war the president was revealed to have taken cash bribes from the enemy and deliberately, but surreptitiously, undermined the war effort, resulting in the death of American soldiers. Treason and bribery are enumerated impeachable offenses; assuming that the facts were clear, this is about as easy a case of impeachment as could be imagined. But now imagine that these facts come to light only a week before the president's term is due to expire, after losing reelection. It is hard to say that the House would be under any sort of obligation to impeach, rather than waiting for the president to leave office naturally.

This scenario is extreme in both directions, but it demonstrates that the House may properly take into account these sorts of prudential considerations. This accords with the House’s role in the process, which is often compared to that of a grand jury, but which is also analogous to that of a prosecutor. (For example, on the one hand, the House appoints the impeachment managers, who present the case for removal to the Senate. A criminal grand jury, on the other hand, does not choose who will present the case against a defendant at trial.) And prosecutors routinely exercise discretion about whether to pursue cases even if there is enough evidence to convict. Nor is timing the only valid ground on which the House can exercise its prosecutorial discretion. Imagine, for instance, a president who courageously decided to expose their own misconduct in the face of attempted blackmail. The misconduct might well be gross enough to warrant impeachment, considered in a vacuum, and yet the House might feel that the president should be rewarded for showing integrity and placing the national interest ahead of their own. Or perhaps, in a marginal case, the House might simply conclude that impeachment is not worth its disruptive impact on the nation.

In these cases the House might employ some other method to express its disapproval of the president’s actions, perhaps a resolution of censure explaining both why those actions could have warranted impeachment and the House’s reasons for deciding against that course.

Finally, may the Senate acquit against the evidence? The answer here is no, but that does not tell the whole story. The practical considerations that may properly play a role in the House's decision should not factor into the Senate's verdict. Consider the same hypothetical as in the previous scenario. If the House did impeach this traitorous president with just a few days left in their term, I do not think the Senate could properly refuse to hold a trial on the basis that it was unnecessary. Nor, of course, would senators be justified in voting to acquit, if the trial could be completed before the president left office. (There is some reason to think that even former officials may be impeached, in which case the trial would not necessarily have to end upon the end of the impeached president’s term.) If the House is the prosecutor and the grand jury, the Senate is both the judge and the petit jury, neither of which typically exercises the same unbridled discretion as a prosecutor. Once the House has determined to bring a case, the Senate’s role is simply to try that case.

Now, trial juries do have what is known as the power of “jury nullification.” Once a jury has acquitted, no judge can overturn that verdict. And throughout our history, there have been many examples—some heroic, some decidedly not—of juries using this power to frustrate prosecutions they viewed as unjust, even if the evidence suggested that the defendant was guilty of the offense charged. If the Senate is a jury, why should it not exercise this same power?

The answer is that the Senate has no need of the power to nullify, because it is already empowered to render its own judgment as to whether the president’s conduct warrants removal. The Senate is not bound by the House’s judgment in this regard—it is judge as well as jury, as Senator Tom Harkin insisted during President Bill Clinton’s impeachment trial. To be sure, there may be cases in which the Senate could not reasonably acquit, such as the earlier treason-and--bribery hypothetical. These can be thought of as “mandatory” impeachments: If the Senate believes, as a factual matter, that the president has committed certain offenses, it has no discretion, and must convict.

But there is also a wide range of what could be termed “discretionary” impeachments. In this zone, even after being convinced of the facts charged by the House, the Senate must make a decision about whether those facts rise to the level of an impeachable offense. Suppose the president has obstructed justice as to some relatively minor matter—say, by helping a personal friend escape prosecution for a white-collar crime in which the president was not involved. It is hard to say that the House would be wrong to deem this impeachable, as a violation of the president’s duty to “take Care that the Laws be faithfully executed.” But it is equally hard to say that the Senate would be wrong to conclude that this was just not a big enough deal to constitute a high crime.

There may also be cases in which the president does something that would be justified by a particular constitutional theory, but that would, if that theory were rejected, clearly constitute an impeachable offense. Here, the Senate must determine not whether the president’s wrongdoing rises to the level of impeachment, but whether those actions were wrong to begin with. Some of President Barack Obama’s executive actions with regard to immigration could arguably have amounted to impeachable conduct on the view espoused by his Republican opponents in Congress. But if he had been impeached over this, Democrats in the Senate would have been well within their rights to acquit, on the grounds that they believed Obama had acted lawfully.

In either of these examples, the House vote to impeach and the Senate vote to acquit could both be entirely proper, as each simply reflects a different judgment about the threshold for impeachment or about the president’s constitutional powers and obligations. And because the Senate is not bound by the House’s judgment, it has no need to acquit against the evidence. Even if the House proves its allegations, the Senate is free to conclude—as a matter of law—that those charges do not warrant removal.

Taking a step back, then, we see that the legal aspect of impeachment operates chiefly as a constraint: Congress may not properly impeach the president without a valid legal basis. But generally speaking, Congress is not legally obligated to impeach. Outside of a narrow zone of mandatory impeachments, both the House and the Senate can make legitimate judgment calls as to whether the president’s conduct is a high crime or misdemeanor. And the House may also consider entirely nonlegal, prudential factors that weigh against pursuing impeachment even when the facts would support doing so.

There is, however, one political factor that neither the House nor the Senate can ever properly consider: raw partisanship. If impeachment is not a no-confidence vote, then it should not be influenced by whether members of Congress generally approve of the job the president is doing. Both the president and the nation are entitled to the same detached neutrality from Congress that we would expect from the judge and the jury in a criminal trial. This applies not only to the Senate, which as noted swears a special oath to do impartial justice in impeachment trials, but to the House as it exercises its prosecutorial discretion. A prosecutor who pursued or declined cases based on the defendant’s political affiliation would have abused their power. Every member of Congress swears an oath to defend the Constitution upon taking office, and impeachment is one of the Constitution’s most important defense mechanisms. The decision whether to invoke this power should rest solely on the national interest, not on partisan interests.

This story is part of the project “The Battle for the Constitution,” in partnership with the National Constitution Center.

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