President Obama on Thursday will welcome Donald Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE to the White House, beginning a transition of power that is pure anguish for many in the Democratic Party.

The meeting, which seemed improbable just 72 hours ago, will likely stand as one of the most humbling moments of Obama’s presidency.

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Trump rose to political stardom in Obama’s first term by questioning his birthplace, spurring Obama to label him a “carnival barker.” The feud carried over into this year’s campaign, where Obama repeatedly described Trump as unfit for the Oval Office.

But despite his efforts, and vigorous campaigning by first lady Michelle Obama Michelle LeVaughn Robinson ObamaMichelle Obama: 'Don't listen to people who will say that somehow voting is rigged' Michelle Obama and Jennifer Lopez exchange Ginsburg memories Social media platforms put muscle into National Voter Registration Day MORE, Trump vanquished Hillary Clinton Hillary Diane Rodham ClintonButtigieg stands in as Pence for Harris's debate practice Senate GOP sees early Supreme Court vote as political booster shot Poll: 51 percent of voters want to abolish the electoral college MORE with victories in swing states that Obama had carried in 2008 and 2012.

Now Obama must begin to hand the keys to the White House to a leader who has pledged to unravel much of his legacy, from ObamaCare to environmental protections to Wall Street reform and the Iran nuclear deal.

“I’m not saying it’s going to be an easy meeting,” White House press secretary Josh Earnest said.

Dark clouds hung over the White House the day before Trump’s visit, mirroring the mood inside the executive mansion.

But the sky cleared before Obama entered the Rose Garden Wednesday afternoon to put a positive spin on the results.

The president recalled a video he recorded on election night, in which he reminded the country that “the sun would come up in the morning” no matter who won.

“That is one bit of prognosticating that actually came true,” he said. “The sun is up. And I know everybody had a long night. I did as well.

“But the day after, we have to remember that we’re actually all on one team.”

While Obama emphasized the importance of a smooth transition and a unified American government, there was no mistaking the pain felt by those on hand.

Dozens of shell-shocked staffers filed into the Rose Garden to watch the statement, including Valerie Jarrett, Denis McDonough Denis Richard McDonoughThe swamp wasn't drained — it expanded Susan Rice calls for Flynn-Kislyak transcripts to be released GOP seeks to go on offense using Flynn against Biden MORE and Susan Rice — all members of the president’s inner circle.

Obama’s team gave him an ovation that lasted for more than a minute after Vice President Biden and he returned to the Oval Office arm in arm.

No two-term president did more than Obama to ensure the election of his preferred successor in Clinton. But her colossal failure on Election Day could result in much of his legacy being wiped away.

Obama cast Clinton as a guardian of his accomplishments, warning voters in stark terms that a Trump presidency would “reverse every single thing that we’ve done.”

Trump has vowed to roll back Obama’s regulations on “day one,” hold a special session of Congress to repeal ObamaCare and “renegotiate” the Iran deal.

He’ll be helped in that effort by Republican majorities in both chambers of Congress. Senate Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellPelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Senate GOP aims to confirm Trump court pick by Oct. 29: report Trump argues full Supreme Court needed to settle potential election disputes MORE (R-Ky.) drove that home Wednesday when he said ObamaCare repeal is “pretty high on our agenda.”

Earnest said Obama would likely not lobby Trump to keep his policies in their meeting, but he suggested it might be riskier for Republicans to forge ahead with repeal of the healthcare law if an increasing number of people lose their insurance.

Obama gave his staff in the Rose Garden a pep talk about continuing the administration’s work.

“I also told my team today to keep their heads up, because the remarkable work that they have done day in, day out … has left the next president with a stronger, better country than the one that existed eight years ago,” he said.

The debate over the meaning of Trump’s win will play out for weeks to come. In the meantime, Obama will have to endure the transition of power to a man he resents.

It all began in 2011, when the real estate mogul stoked false rumors that Obama was not born in the United States and thus ineligible to serve as president. The firestorm grew so heated that the president eventually released his birth certificate proving he was born in Hawaii.

Obama delivered a blistering takedown of Trump at that year’s White House Correspondents’ Association dinner, lampooning everything from his “birther” crusade to his reality TV show.

Even in the final days of the campaign, when Obama’s warnings about Trump escalated, he joked about the prospect of Trump becoming president.

“If we let this thing slip and I’ve got a situation where my last two months in office are preparing for a transition to Donald Trump … even going on [your] cruise won’t help me then,” Obama said in an interview with the radio host Tom Joyner.

“If I’m on the cruise, I might jump off.”