I’m starting to feel left out because I haven’t published a Saturday Night Massacre/Nixon/impeachment take yet. (Seth Masket and I did write this piece on constitutional crisis…) Heavy hitters in the constitutional law world are clearly thinking about the possibility that last week’s events will mark the beginning of the end of the Trump presidency. But despite the fact that the i-word has been trotted out, there’s been less said about the two presidents in American history who actually went through the impeachment process, Andrew Johnson and Bill Clinton.

This absence isn’t that surprising. The Clinton and Johnson impeachments are widely recognized as bogus — trivial acts of political vengeance. Challenging these distinctions requires heavy normative judgments. I won’t shy away from these, but that’s not the purpose of this post. Instead, this would be a good time to ask why this constitutional mechanism has been employed so sparingly and under such controversial conditions — and what this implies for Trump.

Most of us learn about Johnson’s impeachment as a case of partisan politics run amok. Most of the 11 articles of impeachment dealt with the violation of the Tenure of Office Act, which was probably unconstitutional anyway. An additional article of impeachment charged that Johnson had shown disrespect to Congress by engaging in “utterances, declarations, threats and harangues” that demeaned the office and failed to respect the separation between the branches — that is, giving speeches about his conflicts with Congress. It’s not exactly a charge that resonates with modern audiences, although it does make one wonder what the congressional Republicans who impeached Johnson would make of Donald Trump’s tweets. We’ll never know, but just for the record, I would watch that time-travel sci-fi movie.

Johnson came only one vote away from removal in the Senate. None of the Senate Democrats — Johnson’s erstwhile party before joining the Union ticket in 1864 — voted to remove him, but a few Republicans defected. On a biographical note of my own, I remember learning about the deciding vote — Edmund Ross of Kansas — as a sort of tale in political courage. Ross knew the charges weren’t serious and ultimately sacrificed his own career to vote the right way. In her short book about Johnson, historian Annette Gordon-Reed offers a different view:

In a parliamentary system, when the leader loses the confidence of his or her party and the people, the leader resigns his or her position. The country is not forced to endure failed, and potentially catastrophic, leadership until the clock runs out. Imagine an American president who comes into office with the requisite four-year term. Within the first year or so, it becomes apparent that the president is incompetent. He makes a series of grievous mistakes that harm large numbers of people, sometimes resulting in great loss of life. The citizens in the country turn against him — even an overwhelming majority of the voters who put him in office. The president refuses to change course. What is to be done about such a person?

What Gordon-Reed highlights is that the usual story of Johnson’s impeachment only makes sense if we disregard the context of Reconstruction. Major questions of national rebuilding were at stake, and there was substantial violence against African Americans in the South. Johnson vetoed legislation to address these problems.

There’s no need to belabor the Trump-Johnson comparison, which I’ve made before, but there are lessons here. Even if the worst accusations made by Trump’s critics all turn out to be true, the process by which opponents attempt to remove him from office will be highly political. There is no nonpartisan, apolitical mechanism to evaluate abuses of power and remove a president from office. Our Constitution places this responsibility with the people’s elected representatives (and senators, to be precise). The justification for such a choice is strong. The implications, like the people and our representatives, are also imperfect.

It’s harder to figure out what can be learned from the more recent Clinton case. Amid impeachment talk, the Democrats picked up seats in the 1998 midterms, breaking a decades-long pattern of midterm loss for the president’s party. Votes in the House and the Senate largely fell along party lines, with enough Republican defections to prevent Clinton’s removal.

Importantly, although reaction to Clinton’s behavior was heavily filtered through a partisan lens, the whole incident left a strong sense that the office had been brought down. There was much less space for a debate about what that might mean — for the ambiguity of an office occupied by individuals who were flawed, often deeply so, while holding immense power and symbolic significance. Although they were very different episodes, both the Clinton and Johnson impeachments shared a mix of partisan and personal politics and real substantive questions about presidential politics.

When it comes to applying these lessons to the current situation, I can already hear the outrage from both sides. For Trump critics, the real issue is the abuse of power, evident in the firing of a subordinate charged with investigating the Russia connection, the lies to obscure the motives, and the admission that those were lies. Shouldn’t there be an automatic mechanism for impeachment that goes into effect under certain conditions? Maybe there should be. Thing is, there’s not.

From Trump defenders, I expect that objections will cite the president’s legal authority to fire the FBI director, and accuse critics of merely wanting to go after the president because they disagree with his agenda.

The bigger picture here is the impossibility of disentangling our understandings of power, law, and process from substantive worldviews. The presidency itself is central to this dilemma. When it comes to how presidents use power, sometimes the answer comes down to “the end justifies the means.” The deeper the disagreement on the ends, the more contention there will be about whether the means were appropriate.

I obviously have no idea what’s going to happen next. But amid calls for impeachment, we know that this constitutional mechanism has only been deployed a few times, and that the Senate has never voted to remove a president from office. We know that the two times the process has unfolded in full (Nixon resigned before it could proceed), it has overwhelmingly been understood as a matter of partisan politics.

The Constitution leaves little specific guidance about the relationship between the president and Congress. The institutions can hold each other accountable, but only in certain ways. Accountability in general is one of the more fraught concepts in the Constitution, which ultimately prizes stability and insulation from short-term political forces. As the Gordon-Reed quote above suggests, this can mean that holding politicians accountable for their actions can be a slow and clunky process, just as our lawmaking often is.

Instead, the Constitution implicitly places a great deal of weight on two processes for limiting presidential power. First, the design is supposed to ensure that members of Congress have their own bases of political support — districts or states that give them different incentives than other actors. The nationalization of party politics has eroded this.

The briefly outlined but expansive powers of the executive branch — the one whose duties, by definition, include carrying out the law and bringing the Constitution from paper to life — rest on a different assumption. That assumption was that processes would develop around presidential selection in order to choose someone with appropriate qualifications and broad political appeal. This assumption no longer holds, and the opportunities to protect the Constitution this way have passed.

Where does this leave us? A growing number of critics await the moment that congressional Republicans will put the rule of law above politics. But this is at odds with constitutional logic. The main checks on presidential power are found in politics, not in law. History suggests that impeachment is no exception.