Today, President Trump’s cabinet looks more like a revolving door. Since taking office, he has fired an unprecedented number of cabinet members, including his Secretary of State and other key advisors. But if it were the 1860s, the president’s unilateral firings would have been an automatically impeachable offense, thanks to a law intended to restrict presidential powers—a law that almost got a sitting president booted out of office.

The Tenure of Office Act seemed simple—it prevented the president from firing cabinet appointments that Congress had previously approved. But when President Andrew Johnson defied it, a ludicrous standoff resulted. As a result of his combative attempt to skirt the law, Johnson was nearly impeached and has gone down in history as one of America’s worst presidents for his defiance. 

Before the law was passed, presidents could fire cabinet members at will. But the law—created to stop Johnson’s attempts to soften Reconstruction for Southern states after the Civil War—wasn’t just any Congressional act. It resulted in an increasingly absurd spiral of one upmanship that culminated in a rare presidential veto, an even rarer congressional override, a sensational impeachment trial that was so well-attended that Congress had to raffle off tickets, and an ongoing conflict over executive power.