As of 2019, how many incumbent (first-term) U.S. presidents failed to get re-elected?

Five American presidents were unable to win an election and secure a second term in the office. These presidents are: William Taft, Herbert Hoover, Gerald Ford, Jimmy Carter and George Bush, Sr. If reasons for failure are needed, it has been noted that former presidents who serve during times of turmoil, especially when it comes to a domestic recession or difficult economic environment, usually have a difficult time winning re-election. At other times, the presidents were unable to make their marks on history and capture enough popularity to win a second term in office.

President William Taft, the 27th president from 1909 until 1913, needed to be more popular. President Herbert Hoover, the 31st president, served in 1929-1933. The stock market crash of 1929 occurred right after Hoover entered office, and he also faced the Great Depression. President Gerald Ford, the 38th president, failed to win re-election in 1976. In 1974, Ford granted a pardon to Nixon (Nixon resigned over the Watergate scandal); this is a key reason cited for his failure to win re-election. President Jimmy Carter was the 39th U.S. president, and he lost out to Ronald Reagan, who served two terms. Carter served during a struggling U.S. economy and also, his foreign affairs track record was described as uneven. He was not very popular. Lastly, President George H.W. Bush, the 41st U.S. president, also known as Bush Sr., had to handle a struggling U.S economy. He lost to President Bill Clinton.