John Tyler
Because Tyler had not been elected to hold the office of President, some people thought that he lacked a claim to the position. But as the United States Constitution says that the Vice President is vested with the responsibilities of the Presidency in case of "Death, Resignation or Inability" of the former, Tyler said this meant the position was his to fill. A majority of the government agreed and he was sworn in as the new president, however, the Whig Party did not want Tyler, and a lot of Whigs ended up calling him "the accidental president" or "His Accidency".