The peaceful transfer of power from one president to the next is a hallmark of American democracy. After John Adams was inaugurated as second president of the United States in 1797, he wrote to his wife, Abigail, describing George Washington's actions, "When the Ceremony was over he came and made me a visit and cordially congratulated me and wished my Administration might be happy Successful and honourable."

Washington's example set the stage for future U.S. presidents to follow this tradition. Yet that doesn’t mean the actual process has always gone smoothly. In fact, many presidential transitions have been highly uncomfortable affairs, beginning with the first-ever transfer of power between political opponents in 1801. But there have also been gracious moments_—_including a heartfelt letter of support from George H.W. Bush to his successor, Bill Clinton, which launched a new tradition followed by the nation’s most recent presidents.

John Adams chose not to attend the inaugural ceremony of Thomas Jefferson, to whom he lost the brutal election of 1800. Instead, Adams slipped out of Washington on the early morning of Jefferson’s inauguration. Jefferson’s victory marked a complete shift of power in the young nation from the Federalists to Jefferson’s Democratic-Republicans, in what Jefferson called “the revolution of 1800.”

Four years after winning the popular vote but losing the White House thanks to the “corrupt bargain,” Andrew Jackson defeated John Quincy Adams in an 1828 campaign marred by mudslinging on both sides; Jackson even blamed the Adams camp’s attacks for contributing to the death of his wife, Rachel.

On Inauguration Day, Adams followed his father’s example, leaving town before the ceremony. A mob of some 20,000 people flooded into the White House to shake the hand of the new “Frontier President,” causing such chaos that Jackson himself was forced to flee through a side door.

Jackson and his successor, Martin Van Buren, rode to the Capitol in the same horse-drawn carriage for Van Buren’s inauguration, setting a new example for peaceful transitions. Most outgoing presidents after Jackson would follow the same custom—but there were exceptions. Andrew Johnson declined even to attend the inauguration of his successor, Ulysses S. Grant, instead deciding to remain in the White House and conduct a final meeting of his Cabinet.

The 1932 election occurred during the worst economic downturn in the nation’s history. FDR defeated Herbert Hoover in a landslide, promising “a new deal for the American people.” After the election, Hoover repeatedly attempted to get Roosevelt to work together to confront the economic crisis, but Roosevelt refused, as acceding to Hoover’s conditions would have fatally weakened his planned New Deal before it began. Roosevelt would be the last incoming president with a transition that lasted until March: The 20th Amendment, ratified soon after he took office, moved Inauguration Day to January.

The two men worked together in the last months of World War II, as well as during the creation of NATO, but their relationship deteriorated during the 1952 election, in which Eisenhower defeated Adlai Stevenson. Truman was horrified by Eisenhower’s use of hardline anti-Communist rhetoric in his campaign, especially his refusal to denounce Joseph McCarthy. On Inauguration Day, Eisenhower refused to enter the White House, waiting outside for Truman in the car before they rode to the Capitol together. According to presidential adviser Clark Clifford, “The hatred between the two men that day was like a monsoon.”

During the tumultuous election of 1968, the country’s divisions_—over civil rights and the ongoing Vietnam War, among many other issues—_played out in stark relief. Shortly before the election, Johnson learned that Nixon’s campaign had been conducting secret negotiations, through intermediaries, to discourage the South Vietnamese government from participating in peace talks favored by the Johnson administration. Though Johnson considered such actions treasonous, he declined to expose Nixon’s involvement in the scandal. Not only did he lack definitive proof of Nixon’s direct involvement (though such evidence ultimately emerged), he believed the nation would suffer if a president-elect were revealed to have taken such actions, and he saw national security as paramount given ongoing tensions with the Soviet Union.

Economic woes and the Iran hostage crisis doomed Jimmy Carter’s hopes for reelection in 1980. On January 20, 1981, minutes after Ronald Reagan was inaugurated into office, 52 U.S. diplomats and citizens were released from the U.S. Embassy in Tehran, where Iranian student revolutionaries had held them hostage for 444 days. According to Reagan biographer Richard Reeves, by the time Carter and Reagan shared a limousine ride to the Capitol on Inauguration Day, Carter hadn’t slept in 48 hours due to last-minute negotiations of their release. Later, allegations were made of a backroom deal between the Reagan campaign and the Iranian government to delay the hostages’ release until after his election and inauguration, but these weren’t substantiated.

Some past presidents had left letters for their successors, but the one left by George H.W. Bush for Bill Clinton went down in history as one of the most gracious, and launched a new tradition for outgoing U.S. presidents. Though Clinton had defeated his bid for reelection in 1992, in a race that also featured the third-party candidate Ross Perot, Bush sought to reach across partisan divisions and offer a message of support to his successor.

“Your success now is our country's success. I am rooting hard for you,” Bush wrote at the end of the letter, which went viral on social media around the time of Bush’s death in 2018. Clinton would continue the tradition, as would Bush’s eldest son, George W. Bush, and Barack Obama.