I agree wholeheartedly with Pete regarding the remarkable relationship that developed between Adams and Jefferson after the bitter election of 1800. The letters between them in their old age are fundamentally important primary historical source material, and unlike a lot of important historical source material, they are a pleasure to read.
There are two other remarkable things about the election of 1800. It was, as far as I know, the first time in all history that a head of state was defeated in a popular election and accepted, without resistance, the decision of the electorate. On March 4th, 1801, John Adams left the White House and began his journey back to his home in Massachusetts by public coach. Today, such an event is commonplace, at least in the United States if not the Third World where democracy has often turned out to operate under the principle of one man, one vote, one time. In just the last 35 years no fewer than three presidents have been turned out of the White House by the people and simply went home (although in fancier transportation than a public coach). But in the world of the Founding Fathers, Adams’s action set a powerful precedent. No wonder the European intellectuals of the time regarded the American experiment in self-governance as so astonishing.
The other hero of the election of 1800 is Alexander Hamilton. Through a flaw in the design of the Constitution (they didn’t make many!) later corrected by the 12th Amendment, Thomas Jefferson and Aaron Burr (the Jeffersonian candidate for vice president) tied in the Electoral College, throwing the election into the House of Representatives. Hamilton, who had clashed repeatedly and deeply with Jefferson while they both were members of George Washington’s cabinet, had no love for the Virginian. But Hamilton had no respect for the utterly amoral Burr. A pettier man might have used his considerable influence with Federalist members of the House to deny Jefferson the presidency out of spite. But Hamilton did no such thing. He urged his followers to vote for Jefferson. It was the noblest moment in Hamilton’s public career. It could be argued, I suppose, that it even cost Hamilton his life. The most famous duel in American history would never have taken place if Burr had been president.