Republicans in Congress face a desperate dilemma. The President, ostensibly their ally, has proven increasingly erratic and hard to control. He acts with minimal regard for the law, lashes out at his Cabinet, and seems determined to tear down everything his predecessor worked so hard to build. The year is 1868, and Congress decides to bring Andrew Johnson to heel with the greatest weapon at their disposal: impeachment.

As the situation in Washington grows more fantastic by the day, modern Americans are understandably becoming more interested in how impeachment works. The mechanics are relatively simple, but what triggers impeachment is much fuzzier. The Constitution empowers Congress to impeach and remove the president for "treason, bribery, or other high crimes and misdemeanors." The first two are pretty clear, but that last clause gives legislators a lot of leeway. By examining the first time Congress used its impeachment powers, we can get a better sense of what conduct might lead to impeachment, along with how the process unfolds.

Protesters call for impeachment

Andrew Johnson became President on April 15, 1865, upon the assassination of Abraham Lincoln. The military governor of Tennessee during the Civil War, Johnson was chosen by Lincoln as his 1864 running mate as a symbol of union, a Southern Democrat joining an administration of Northern Republicans. Johnson had been a firm supporter of the Union through the war, and upon his ascent to the presidency he sought to bring the southern states back into the Union with minimal conditions, in the name of rapid reconciliation.

Congress, meanwhile, along with most of Johnson's inherited cabinet, believed that the war's outcome showed a clear verdict: the Confederacy had been defeated, and with it not only slavery but the whole of the old racial caste system. A new South would be built on the basis of racial egalitarianism, with the federal government taking a strong hand to ensure that freed slaves had access to jobs, land, and the ballot. This was unacceptable to Johnson, who spent the bulk of 1866-7 using every power at his disposal, most notably the veto, to block Congress's plans. He vetoed a bill authorizing the Freedman's Bureau (designed to provide aid and education to former slaves), multiple incarnations of the nation's first civil rights bill, and a host of other proposals. The huge Republican majority in Congress overrode most of these, but the battle lines were clearly drawn.

Congress convenes to discuss the fate of President Johnson

The final straw, from Congress's perspective, was Johnson's decision to fire his Secretary of War, Edwin Stanton. With the South still under military jurisdiction following the war, Stanton had broad powers over how the occupied states were governed. The generals he oversaw as military governors were instructed to protect the rights of freedmen, and troops under his command had put down riots, lynchings, and even attempted coups by the Klan and other white supremacist groups. Johnson saw this as an unlawful assault upon the rights of southern whites, and wished to replace Stanton with someone friendlier to their cause. To prevent precisely this sort of action, Congress had earlier passed the Tenure in Office Act, barring the president from removing any Senate-approved appointee unless the Senate agreed. Johnson fired Stanton anyway, and the House approved articles of impeachment.

The House quickly impeached Johnson along party lines, the trial went to the Senate, and at this point the complicated nature of impeachment became clear. Johnson's lawyers argued that the Tenure Act didn't apply to Stanton, since Lincoln had appointed him and Johnson had only inherited him. Some moderate Republicans worried about the unprecedented nature of a successful impeachment. Still others worried about the line of succession, since Johnson had no Vice President and the man next in line supported such wild causes as labor rights and women's suffrage. With political considerations ruling the day, Johnson was acquitted by a single vote, and remained in office. He didn't last long, as neither the Democrats nor Republicans nominated him for the 1868 election, and he was succeeded by Ulysses Grant.

Johnson's impeachment, far more than that of Bill Clinton, reveals the bizarre nature of the process. While there was a clear legal basis for the impeachment, the underlying cause was obviously political. Johnson was using his powers as President to thwart the express wishes of Congress, arguably in favor of a class of people who had just committed mass treason. He was also, to put it plainly, something of a political embarrassment. Eric Foner describes his speech following the veto of the Freedmen's Bureau as "self-absorbed (in a speech one hour long he referred to himself over 200 times), intolerant of criticism, and out of touch with political reality." (Sound familiar?)

Of course, because impeachment is political, the rules we tend to associate with crimes, trials, and verdicts don't really apply. Andrew Johnson clearly violated a law, and as an accidental president had trouble making the traditional argument that he was the true voice of the people against an overreaching Congress. And still he stayed in office, because the political question was more complicated than simple guilt or innocence. Similarly, no one remotely credible believed that Bill Clinton hadn't lied under oath, but relatively few Senators saw this as being serious enough to warrant removal from office.

Where does that leave things, 150 years almost to the day after Johnson's trial began in the Senate? Clearly, an impeachment of the current president is a non-starter with a Republican majority in Congress. But should the midterm elections go as they're expected to, what then? Would what we already know about this administration suffice to begin the process? Will Robert Mueller survive the threat of dismissal long enough to provide substantive charges? Would the Senate follow through? Here we can consider the third historical example: Richard Nixon, who resigned his office when it became clear he wouldn't have the votes to survive an impeachment. So perhaps there's a way out without the difficulty and uncertainty of impeachment. It simply requires Donald Trump to have the humility and grace of Richard Nixon.