The Basic Story
When we think of constitutional crises in American history, usually the first thing that comes to mind is the Watergate scandal and its aftermath. The notion that a President of the United States had engaged in criminal activity, virtually inconceivable just a few years before, was viewed as reality in 1974. And while President Richard Nixon's resignation would put an end to that crisis, the American people have viewed the presidency in a far different light ever since.
Nixon's resignation would spare the nation his certain impeachment by the House of Representatives, and almost as certain conviction by the United States Senate, resulting in the first removal of a President from office. A successor, Bill Clinton, would not be spared impeachment in 1998, but would be acquitted; as would our 17th President, Andrew Johnson.
Almost immediately upon ascending to the presidency following the assassination of Abraham Lincoln, Johnson took a confrontational posture toward Congress, regularly using his veto power in an effort to thwart its efforts to influence Reconstruction in the wake of the Civil War. When overriding Johnson's vetoes failed to dissuade him from using the practice, Congress decided to begin passing legislation aimed at curbing his executive power. One such law, the Tenure of Office Act of 1867, imposed a new restriction on the President, prohibiting him from removing Cabinet officers from their service without Senate approval, and from suspending such officers if the Senate was not in session. When Johnson vetoed the act, as it had with several other acts Congress voted to override - yet another slap.
That summer, in his first opportunity to do so, President Johnson decided to test the constitutionality of this law. With the Senate adjourned for the summer, Johnson suspended Secretary of War Edwin M. Stanton from his service. On January 4, 1868, the Senate countered by refusing to ratify Stanton's permanent removal by a 35-16 vote. The President, meanwhile, responded by sending the Senate written notice appointing future President Ulysses Grant as his successor. Johnson saw it as a means toward taking the matter to federal courts for resolution. The Senate meanwhile saw it as the last straw.
For the first time in American history, on March 2, 1867 the House of Representatives approved articles of impeachment against the President of the United States. Eleven articles, to be precise; ten of which were directly related to the circumstances surrounding the Tenure of Office Act. Tried by the Senate, on May 16th the Senators voted on the eleventh and final article. Needing a two-thirds majority to convict and remove President Johnson from office, they fell one vote short at 35-19. Having failed to convict on what they thought would be the only ballot they needed, those wanting Johnson's ouster adjourned and regrouped. Ten days later, the Senate reconvened and voted on the second and third articles. The result was the same, 35-19, with not one vote changing.
A Near Congressional Coup d'etat
Aside from the fact that we came one vote in the United States Senate away from removing Andrew Johnson as President, why could this be seen as a Congressional coup d'etat? Because of the man who would have replaced him had that vote not gone Johnson's way. As Andrew Johnson had ascended to the presidency following the death of Abraham Lincoln, there was no Vice President waiting in the wings during the President's impeachment trial.
In accordance with the Presidential Succession Act of 1792, Senate President Pro Tempore Benjamin Franklin Wade was next in the line of presidential succession. Meanwhile, Wade was among those who had advocated - and in the Senate, voted for - Johnson's conviction and removal. So, had Johnson been convicted by a 36-18 margin rather than acquitted by a 35-19 vote, Wade not only would have entered the White House - he'd have done so as the result of his own vote. The potential ramifications of this - essentially shattering the separation of powers and permanently subordinating the executive branch to the legislative, wasn't lost on one man: Kansas Senator Edmund Ross.
The Man Who Saved the Republic. Sort of.
Throughout the course of the impeachment trial, Senator Edmund Ross had been undecided on the question of conviction. A Republican, Ross had several concerns: about whether a President has a right to replace Cabinet officers at will, whether Johnson's defiance was an act worthy of removal from office, and about the idea of Benjamin Wade becoming Acting President of the United States. Ross also contemplated the need to remove a President who was so unpopular that re-election later in 1868 was unfathomable; in short, why remove a President who'd be gone in ten months anyway? There's also a distinct possibility that Ross was simply bribed by Johnson supporters for his vote.
But regardless of his reasons, at Ross' moment of truth he joined six other Republican Senators who voted for acquittal; a decision he'd stick to on each of the three articles considered by the Senate. Seeing that the vote had gone unchanged on the three articles voted upon to date, as May 26 came to its conclusion trying to kick Johnson to the presidential curb again decided to pause and regroup. This time however, they never bothered to revisit the subject of the President's removal. The remaining eight articles of impeachment went unacted upon, and with the adjournment of the 40th Congress on March 3, 1869 - one day before Johnson would be succeeded by Ulysses Grant as President - the impeachment matter was formally concluded without further action.