WASHINGTON — It took all of one minute and nine seconds for President Trump to go after his predecessor on Friday — just one minute and nine seconds to re-engage in a debate that has consumed much of his own time in office over who was the better president.
It was former President Barack Obama who started the policy of separating children from their parents at the border, Mr. Trump claimed falsely, and it was Mr. Obama who had such a terrible relationship with North Korea that he was about to go to war. Mr. Obama had it easy on the economy, Mr. Trump added, but let America’s allies walk all over him.
The litany of criticisms, often distorted, are familiar, but Mr. Trump has turned increasingly to Mr. Obama in recent days as a political foil.
In part, that reflects Mr. Trump’s longstanding fixation with the former president. But it may also stem from the fact that Mr. Obama’s vice president, Joseph R. Biden Jr., remains the Democratic front-runner in the 2020 election.
“If you look at what we’ve done, and if you look at what we’ve straightened out, the — I call it the ‘Obama-Biden mess,’” he told reporters on the South Lawn of the White House before leaving Washington for a weekend at his golf club in Bedminster, N.J. “We’re straightening it out.”
The president’s focus on Mr. Obama after about two and a half years in office was even more intense during a trip to Japan and South Korea last weekend, when Mr. Trump repeatedly raised the subject of his predecessor without being asked, assailing him on a variety of domestic and foreign policy fronts.
“When in a corner, Trump falls back on the only organizing principle he has, which is attacking Obama — and usually lying about it,” said Benjamin J. Rhodes, a former deputy national security adviser to Mr. Obama. “I wouldn’t read anything more into it than that.”
Since 2011, when he explored running for president against Mr. Obama, Mr. Trump has had a singular obsession with the 44th president.
He repeatedly questioned Mr. Obama’s citizenship as part of the false “birther” conspiracy. As president, Mr. Obama struck back at the White House Correspondents’ Association dinner in 2011, when he roasted the reality television star as a lightweight while Mr. Trump sat grim-faced.
Since then, Mr. Trump has been determined to minimize or unravel Mr. Obama’s accomplishments, and lately has even suggested that his predecessor was behind a deep-state conspiracy with law enforcement and intelligence agencies to thwart his 2016 candidacy.
While other presidents have blamed their predecessors for various national ills — including Mr. Obama, who in his first term regularly pointed to former President George W. Bush — Mr. Trump takes it further than most.
It is less common for presidents to take on predecessors who are more popular than they are; Mr. Obama was viewed favorably by 63 percent of those surveyed by Gallup last year, while Mr. Trump’s job approval rating is 41 percent.
But Mr. Trump recognizes that his political base wanted, and still wants, someone who would be seen as fighting against Mr. Obama. Especially as Mr. Biden stumps the country on his record in the Obama administration, Mr. Trump sees a political advantage in taking down his predecessor and trying to lift himself as an outsider taking on a system he has led for over two years.
“Tell Biden that NATO has taken total advantage of him and President Obama,” Mr. Trump said on Friday. “Biden didn’t know what the hell he was doing and neither did President Obama. NATO was taking advantage of — now they’re paying.”
“President Obama and Vice President Biden,” he added, “they didn’t have a clue. They got taken advantage of by China, by NATO, by every country they did business with.”
By Mr. Trump’s indictment, Mr. Obama was too soft on China’s trade abuses and too easy on NATO allies who were not spending enough on their own defense, two issues that the current president has pressed much more vigorously. Mr. Trump in recent days has also blamed Mr. Obama for a dispute with Turkey, a NATO ally, over its purchase of S-400 missile systems from Russia. A former Obama aide denied that he refused to sell a Patriot system to Turkey but did object to a technology transfer Ankara demanded as part of a deal.
In leveling his criticisms at Mr. Obama, however, Mr. Trump routinely stretches the facts. As he has repeatedly, Mr. Trump insisted on Friday that had Mr. Obama remained in office, he would have gone to war with North Korea, a claim dismissed as ludicrous by the former president’s advisers.
In recent days, Mr. Trump has added a new claim — that Mr. Obama tried to meet with North Korea’s leader Kim Jong-un, only to be rebuffed, an assertion for which he offered no evidence.
“He called Kim Jong-un on numerous occasions to meet. President Obama wanted to meet with Kim Jong-un. And Kim Jong-un said no,” Mr. Trump said on Friday. “Numerous occasions he called. And right now we have a very nice relationship.”
After Mr. Trump floated this while in Asia last weekend, Mr. Obama’s final national security adviser, Susan E. Rice, used an expletive to deny it. “At the risk of stating the obvious, this is horse-sh*t,” she wrote on Twitter, asterisk and all.
Mr. Rhodes, her deputy, repeated the denial on Friday. “There is zero truth to the claim about wanting to meet Kim,” he said. “It’s completely made up and totally incoherent with his previous claim that Obama wanted to go to war with North Korea.”
Other former Obama-era officials have publicly disputed the notion as well, including James R. Clapper Jr., who was director of national intelligence; Wendy R. Sherman, who was under secretary of state; Daniel R. Russel, who was assistant secretary of state for East Asian and Pacific affairs; and Jeremy Bash, who was chief of staff at the C.I.A. and later the Pentagon.
Mr. Trump has also sought to rewrite the history of his own family separation policy at the border, telling audiences that it was Mr. Obama who started it and the current president who stopped it.
“President Obama built those cells. They were in 2014,” Mr. Trump said last weekend at a news conference in Osaka, Japan. He added, “I just say this: They had a separation policy. Right? I ended it.”
He was correct that the Obama administration built some of the detention facilities that have been at the center of the latest furor over the treatment of migrants detained at the border, but they were never meant for the long-term detention of children.
Moreover, while the Obama administration did break up families, it was relatively rare and typically in cases of doubt about the relationship between a child and an accompanying adult.
Mr. Trump’s administration announced a “zero tolerance policy” in April 2018 that resulted in nearly 3,000 children being forcibly separated from parents. After an outcry, Mr. Trump signed an executive order two months later directing officials to end the practice of family separation.