According to U.S. News and World Report, a few of America's worst presidents were George W. Bush, Richard Nixon, Herbert Hoover, William Henry Harrison, Ulysses S. Grant and John Tyler. This list combined the results of five presidential ranking polls.
Poor economic-decision making and failure to preserve the Union prior to the Civil War were two of the major criteria used by U.S. News and World Report in compiling its list of the worst presidents ever. George W. Bush started off with very high poll results after 9/11 but gradually lost steam as the Iraq War left Americans disillusioned and the Great Recession began in 2008.
Richard Nixon's involvement in the Watergate scandal forever tainted his reputation, and presidents such as Warren G. Harding and Herbert Hoover were considered failures because they contributed to what became the Great Depression. William Henry Harrison died after only a month in office, and John Tyler lost the support of the Whigs after coming out in support of slavery.
Millard Fillmore, Franklin Pierce, Andrew Johnson and James Buchanan rounded out U.S. News and World Report's list. Fillmore, Pierce and Buchanan did nothing to prevent the Civil War, only contributing to the cycle of events that resulted in the dissolution of the Union. Johnson was the first president to be impeached; he lost congressional support after failing to sufficiently punish the former Confederate states.