Though you won’t find him in the National Portrait Gallery, David Rice Atchison just might have been President of the United States for one day. Due to the timing of Zachary Tyler’s inauguration, Atchison claimed he was technically president on March 4, 1849.
David Rice Atchison’s claim to the presidency comes thanks to a combination of two things: fear and bureaucracy. In the middle of the 19th century, because of disease and war, imminent death loomed even for the world’s leaders. Should a president become ill or die, there was (and is) always a backup plan, and then a backup plan to the backup plan. In other words: a line of succession.
With that in mind, the story starts with the inauguration of the president-elect Zachary Tyler. Just like with today’s elections, there was a gap between when a new president was elected and when he was inaugurated (or officially given the job). During that era, inaugurations happened on the March 4 following an election. In 1849, March 4 fell on a Sunday, and Tyler refused to do his inauguration on a Sunday. It had to wait until Monday. That left a one-day gap between the outgoing president and Tyler’s inauguration. In any other circumstance with a missing president, the vice president would assume office. That was impossible, of course, because he too was leaving office.
That’s where the president pro-tempore enters the equation. The position is elected by the Senate and is usually meant to take the place of the vice president in temporary circumstances (i.e. when they can’t make it to a senate session). At the time, it was also the position that follows the vice president in the line of presidential succession. Atchison was the president pro-tempore - elected on March 2, 1849, just two days prior to Tyler’s scheduled inauguration. His “claim” to the presidency rests on that short gap between March 4 and March 5.
The plaque on his statue in Plattsburg, Missouri, reads: “President of the United States for one day,” but most historians refute that Atchison was ever technically president. That didn’t stop him from saying that his “administration” was the “honestest...this country has ever had.” Atchison was also a pro-slavery Democrat.