Son of the second president, to whom he owed his formidable intellectual training, John Quincy Adams was fated, like his father, to serve an undistinguished term as president (1828-32). Despite his long experience as an ambassador, senator, and secretary of state, Adams was unable to master the fractious sectional politics of the 1820s. The rigid and humorless New Englander was also out of step with the new popular political style pioneered by Andrew Jackson. Yet these so-called flaws contributed to Adams's success in his life's second act. Returning to Congress in 1831 (the only ex-president to take a lesser office after leaving the White House), Adams became known as "Old Man Eloquent" for his passionate opposition to slavery. In defending the African prisoners on the slave ship Amistad, he made the case in Congress that slavery was not just immoral but unconstitutional.