President Trump’s attacks on the election of Joe Biden are unprecedented, but bitterness over losing is nearly as old as the presidency.

Since George Washington handed the keys to John Adams, the transfer of power between presidents has been complicated, sometimes spiteful and occasionally harrowing, but it has ultimately always been peaceful.

Sure, the country is best served if incoming and outgoing teams play nicely together, experts say. But some of the most successful U.S. presidents overcame rocky transitions and lousy relationships with their predecessors.

Here’s how the process is supposed to go, according to law and tradition:

Before the election

U.S. law requires that the current administration prepare to help potential newcomers before the election, starting by designating a federal transition coordinator to oversee the process. A White House council plans and guides the transition; another council of career officials from federal agencies prepares key information to share.

Meanwhile, most candidates form a transition team long before they receive their party’s formal nomination. These teams coordinate with their campaigns but work separately, setting priorities, drafting lists of job candidates and figuring out how to turn campaign promises into legislation. Biden’s team is co-managed by Ted Kaufman, who, as a U.S. senator, wrote some of the current transition law.

After the conventions, the transition teams of major-party nominees get government office space, secure computers and other support, although the Biden team’s space has gone largely unused because of the pandemic. Finally, the administration and the nominee’s transition team sign a “memorandum of understanding” formalizing how they will work together.

All that happened as planned this year with relatively little drama.

Then came the election.