The first "accidental president," whose secret maneuverings brought Texas into the Union and set secession in motion

When William Henry Harrison died in April 1841, just one month after his inauguration, Vice President John Tyler assumed the presidency. It was a controversial move by this Southern gentleman, who had been placed on the fractious Whig ticket with the hero of Tippecanoe in order to sweep Andrew Jackson's Democrats, and their imperial tendencies, out of the White House.

Soon Tyler was beset by the Whigs' competing factions. He vetoed the charter for a new...