But the animosity between the two men is deep. The Republican made his name in politics by questioning, without evidence, whether America’s first black president, born in Hawaii, was eligible for the office. Obama told adoring crowds on the campaign trail for Democrat Hillary Clinton that it would be an “insult” if Trump replaced him.

On Sunday, Obama offered a guarded response when asked how he could be certain Trump would be more moderate as president than he campaigned.

“I can’t be sure of anything,” he said. “Like everyone else, we’ll have to wait and see.”

Behind the scenes, Obama’s entourage exhibited a dark mood over the course of the week-long trip, during which Trump announced key appointments that alarmed many Democrats and showed ambivalence about separating his business interests from the presidency.

White House aides appeared despondent at times on the trip, particularly after Trump announced he would nominate Alabama Senator Jeff Sessions for attorney general, Representative Mike Pompeo of Kansas for CIA director, and retired Lieutenant General Michael Flynn as national security adviser.

Sessions is an immigration hard-liner whose nomination for a federal judgeship was derailed 30 years ago after he was accused of making racist statements. Pompeo has said that fellow Republicans investigating the death of the Libyan ambassador in Benghazi went too easy on Clinton. Flynn regards Muslim terrorism as an existential threat and has said that Islam is “like cancer.”

Obama’s press secretary, Josh Earnest, and deputy national security adviser, Ben Rhodes, typically hold briefings for reporters during foreign trips. This time, there were no briefings, and the two men eschewed their usual interactions with reporters.

Obama’s own sorrow over the election outcome could only be inferred. At a forum for young Latin American leaders on Saturday, he said that democracy can be “frustrating” and “it means that the outcomes of elections don’t always turn out the way you would hope. And then you - we’re going through that in the United States, and I’m doing everything I can to help facilitate a successful transition with the president-elect in the United States.”

Two days earlier, in Berlin, Obama demurred on a question about whether his close ally, German Chancellor Angela Merkel, should stand for election to a fourth term next year.

“If I were here and I were German, and I had a vote, I might support her,” Obama said. Cognizant of anti-establishment sentiment that seems to be sweeping the globe, and of Clinton’s own loss despite Obama’s assistance, he added: “But I don’t know whether that hurts or helps.”

Obama leaves office in January. He faces extraordinary pressure from fellow Democrats, many of whom are protesting Trump’s election and are concerned that his Republican successor will implement promises from his campaign to deport undocumented immigrants en masse, bar immigration from Muslim countries and encourage aggressive policing and intelligence activities.

If Obama remains involved in the political sphere, it would mark a departure from his recent predecessors. Republican George W. Bush has never commented on his successor’s policies. Democrat Bill Clinton was equally silent on Bush after leaving the White House, though he actively campaigned for his wife, former Secretary of State Hillary Clinton, in her bids for the White House.

“President Bush could not have been more gracious to me when I came in,” Obama said before returning to Washington. “My intention is to certainly for the next two months, just finish my job and then after that to take Michelle on vacation, get some rest, spend time with my girls and do some writing, do some thinking.”

In his parting news conference on Sunday, Obama made a case for American exceptionalism that was just as much a plea to his successor.

“The American president and the United States of America, if we’re not on the side of what’s right, if we’re not making the argument and fighting for it even if sometimes we’re unable to deliver at 100 per cent, then it collapses,” Obama said. “There is nobody to fill the void. There really isn’t.“