John Adams was elected President in 1796, defeating Thomas Jefferson by only three votes (and as per the law at that point, Jefferson was thus named Vice President).
The majority of Adams' single term as President was marked with capable leadership, honesty and utter lack of scandal. For this reason alone it seems that he should be viewed among the top presidents of all time.
Perhaps the most important part of Adams' Presidency, however, was the "quasi-war" fought with France during the majority of his term (see the Suite101 article, "The XYZ Affair" for more information).
As a result of the war led the Federalists in congress to initiate a now infamous set of laws known as the "Alien and Sedition Acts." These acts sought both to curb dissent and to dissuade heightened immigration into the United States.
Many people, specifically the Jeffersonian-Republicans who opposed the Federalists, viewed these acts as being unconstitutional - directly opposing the first amendment rights. Nevertheless, the acts were signed by Adams in 1798, right at the beginning of the Quasi-War. And thus, some might say, was the beginning of the end for the Adams presidency.
While the party of Thomas Jefferson (who were traditionally sympathetic to the French) may have been harmed somewhat by the actions of their "allies" during the quasi-war, the Federalists were hurt much more by the passing of these unpopular acts.
The second nail in Adams' political coffin came from the sudden opposition by a former ally, Alexander Hamilton, due to Adams' refusal to agree with many of the military positions of the "high Federalists," as the party leadership came to be known.
While Adams failed to win reelection to the Presidency in the election of 1800 (see the Suite101 article on "The Election of 1800" for more information on this truly remarkable campaign), he was able to take one final stab at securing a legacy of strong Republican/Federalist values by appointing several "midnight judges" in the final days before the expiration of his term.
While Jefferson and the Democratic-Republicans who were to follow Adams into power were unable to unseat many of these judges, the most important remained - Chief Justice of the Supreme Court John Marshall, who was to be one of the great Chief Justices of all time, and remain a Federalist voice in American Government long after the party itself had all but expired.
As John Adams retreated from public life, he moved back to his old home in Quincy, Massachusettes, where he continued to be a capable political mind, reviving his old friendship with Jefferson in 1812 and beginning a long and famous series of letters back and forth, pondering every topic from politics, to philosophy, to religion.
John Adams, though mired in controversy at the time, has shown through the lens of history to have been a capable and honest President; a defender of Republican values; and a model for the leaders to come.
References:
McCollough, David. "John Adams." Simon & Schuster. 2001.
"Biogaphy of John Adams." The Whte House.