Who was David atchison?

David Atchison was an American politician and lawyer who served as a U.S. Senator from Missouri in the mid-19th century. He is best known for his brief tenure as President pro tempore of the Senate, during which he claimed to have been President of the United States for a single day in 1849, due to the absence of both the President and Vice President. Atchison was a prominent supporter of the pro-slavery cause and played a significant role in the events leading up to the Civil War, particularly in the conflict over Kansas. His legacy is often overshadowed by his controversial political stances and actions.