In a series of tweets early Saturday morning, Trump called Obama a "bad" or "sick" person after accusing him, without evidence, of ordering the government to tap his phones during the 2016 presidential campaign.
While attacks from Trump aimed at Obama are nothing we haven't seen before, they come after months of restraint and even complimentary comments Trump has made about his predecessor since he was elected president. And they marked a return to Trump's earlier treatment of Obama.
The relationship is all best summed up in a comment Trump made on Fox News in late January: "What amazed me is that I was vicious to him in statements, he was vicious to me in statements, and here we are getting along, we're riding up Pennsylvania Avenue. ... We don't even mention it. I guess that's the world of politics."
Here's a look back at some of what Trump has had to say about Obama over the years:
"I want him to show his birth certificate. ... There's something on that birth certificate that he doesn't like." -- Trump on "The View" on March 23, 2011.
Trump launched himself into the national political conversation in March 2011, when he began to publicly question whether Obama was born in the United States -- effectively taking a megaphone to a conspiracy theory that for years had swirled in conservative circles.
"An 'extremely credible source' has called my office and told me that @BarackObama's birth certificate is a fraud," he tweeted on August 6, 2012.
Trump continued to accuse Obama of not being born in the US for several years after Obama released his birth certificate.
"I think he's a threat to our country," Trump said on a radio show.
"Obama is one of the worst negotiators on everything I've ever seen except for when it comes to dealing with the Republicans," Trump said in an interview with NBC News.
"He may be the worst thing to ever happen to Israel, believe me," Trump said at the American Israel Public Affairs Committee's annual conference.
"There's something going on," Trump intoned about Obama in a June interview, suggesting Obama was sympathetic to radical Islamist terrorists.
"You know, people cannot believe that President Obama is acting the way he acts and can't even mention the words radical Islamic terrorism," he said on Fox News. "There's something going on — it's inconceivable. There's something going on."
"I think he's the worst president maybe in the history of our country," said Trump on Fox News.
He also called Obama a "disaster," "weak" and "ineffective" in the interview, echoing many of his criticisms of Obama on the campaign trail.
"ISIS is honoring President Obama. He's the founder of ISIS. He's the founder of ISIS. He's the founder. He founded ISIS," Trump said at an August 10, 2016, campaign rally.
November 10, 2016
Obama is a "good man," Trump said in the Oval Office after meeting Obama for first time.
"Really good meeting, great chemistry," Trump tweeted after meeting with Obama at the White House.
Earlier that day, he told Obama it was a "great honor being with you and I look forward to being with you many, many more times," saying he would seek Obama's counsel.
December 7, 2016
"I must tell you, you know, I never met him before this. I never spoke to him before this. I really -- I do like him," Trump said in interview about his predecessor.
Trump added that he was seeking Obama's advice on appointments and has been taking "his recommendations very seriously."
December 28, 2016
"Doing my best to disregard the many inflammatory President O statements and roadblocks. Thought it was going to be a smooth transition - NOT!" Trump tweeted.
Later, Trump added: "I'm getting along very well with him ... other than a couple of statements (that) I responded to and we talked about it and smiled about it."
"We are never going to be going against each other," he added.
January 22, 2017
"I just went to the Oval Office and found this beautiful letter from President Obama. It was really very nice of him to do that. And I will cherish that," Trump said.
February 6, 2017
"We get along, I don't know if he'll admit this, but he likes me. I like him," Trump said during his Super Bowl interview with Fox News' Bill O'Reilly.
February 27, 2017
"I think he is behind it. I also think it is politics, that's the way it is," Trump said, accusing Obama of being responsible for protests against Republicans.
March 4, 2017
"Terrible! Just found out that Obama had my "wires tapped" in Trump Tower just before the victory. Nothing found. This is McCarthyism!" Trump tweeted, adding, "Bad (or sick) guy!"