James Buchanan(1791-1868), a century and a half after leaving office, seems to have earned himself a near-permanent position near the bottom of the "greatest Presidents" list.
His first and perhaps most grievous error, surely, was in presiding over perhaps the most crucial four years in American history - the four years which led directly to the United States Civil War. It surely would have taken a President of the highest calibre to avoid such a conflict, and Buchanan was certainly not that man.
The early political life of James Buchanan certainly did not foreshadow his eventual political downfall and future infamy. He was born and raised in Pennsylvania, an honors graduate from Dickenson College at 18 years old (after having nearly been expelled for his behavior), and lawyer in his early twenties.
Throughout this time, Buchanan was firmly aligned with the ill-fated Federalist Party, which even at this point was in its waning years, having fielded its one and only President in John Adams, more than a decade earlier.
Buchanan opposed the War of 1812 on ideological grounds, but this did not stop him from serving his country where he was needed, volunteering to aid in the defense of Baltimore when the British invaded Maryland.
In 1814, Buchanan was elected as a representative to the Pennsylvania House of Representatives, where he served four consecutive terms (while still practicing law) until 1819. In 1920, Buchanan won his first term to the U.S. House of Representatives, serving in this capacity until 1831, during which time he served as Chairman of the House Judiciary Committee (due in part to his expertise in Constitutional law).
It was during this time that Buchanan, recognizing that his Federalist party was soon to fade away from the political landscape entirely, was drawn to the politics and personality of Andrew Jackson - founder of what would become the "Democratic" party.
After Jackson won the Presidency in the election of 1828 with Buchanan's help, the up and coming congressman was on Jackson's good side, which resulted in Jackson, after his 1832 reelection, appointing Buchanan to a post as Minister to Russia, where Buchanan was instrumental in drafting a much-needed trade treaty.
By the time he returned to America in 1833, James Buchanan was 41 years old and had already been in public office for 18 years, with no signs of retreating.
Returning to America, Buchanan had won a seat as a Senator under his new "Democratic" (that is, Pro-Jacksonian) banner. In this capacity, he became even more important in Washington politics, chairing the crucial Foreign Relations Committee, which eventually earned him the position of Secretary of State under President Polk (even though Buchanan had desired the Democratic nomination in 1844 for himself).
As Secretary of State, Buchanan played an important role in the territorial expansion authored by Polk, resulting in the Mexican-American War, the purchase of the Oregon Territory, and the Annexation of California.
Buchanan made a strong attempt at the Presidency again in 1852, battling Stephen Douglas of Illinois (future opponent of Abraham Lincoln) for the Democratic nomination. So strong were these two candidates that the party deadlocked in nomination, eventually bringing forth a "comprimise" candidate, Franklin Pierce, to break the stalemate.
Pierce, as a result, won the nomination and the election, appointing Buchanan to the crucial position of Minister to England, where he would become one of the authors of the "Ostend Manifesto," which was a declaration of intent to purchase the territory of Cuba from Spain - a controversial action which would benefit the pro-slavery south by increasing the slaveholding territory of the United States.
Dispite this controversy (one of the many black marks on Pierce's Presidency), Buchanan was well-poised to finally recieve the Democratic nomination in 1856. By this point, however, the sectional crisis had reached a boiling point.
To read about Buchanan's term as President, please see the Article, The Presidency of James Buchanan.
References:
"James Buchanan." American President: An Online Reference Resource.
"Biography of James Buchanan." The White House.