WASHINGTON — President Trump has embarked on an aggressive new drive to rewrite the narrative of the Russia investigation by making dark and unsubstantiated accusations that former President Barack Obama masterminded a sinister plot to bring him down.
On Twitter, on television, in the Rose Garden and even on an official White House social media page, Mr. Trump in recent days has taken aim at his most recent predecessor in a way that no sitting president has in modern times, accusing Mr. Obama of undefined and unspecified crimes under the vague but politically charged catchphrase “Obamagate.”
The president went even further on Thursday by demanding that Mr. Obama be hauled before the Senate “to testify about the biggest political crime and scandal in the history of the USA,” a scenario that itself has no precise precedent in American history. Within hours, Mr. Trump’s most faithful Republican ally in the Senate promptly announced that he would indeed investigate, although he would probably not summon Mr. Obama.
In flinging incendiary charges at his predecessor, Mr. Trump has offered no evidence and has not even specified what “crime” he was accusing the former president of committing. Instead, Mr. Trump seemed to be tying the investigation by the special counsel Robert S. Mueller III, which has enraged him for years, back to Mr. Obama while hinting ominously at forthcoming revelations that will bolster his claims.
In addition to diverting attention from the coronavirus pandemic, Mr. Trump’s focus on Mr. Obama allows him to try to turn the tables on his accusers by making them out to be the ones who are corrupt while simultaneously putting his Democratic challenger, former Vice President Joseph R. Biden Jr., on the defensive.
“This was all Obama, this was all Biden,” Mr. Trump said in an interview on Fox Business Network that aired on Thursday. “These people were corrupt, the whole thing was corrupt, and we caught them. We caught them.”
When the host Maria Bartiromo asked if he believed that Mr. Obama directed American intelligence agencies to spy on him, Mr. Trump agreed, without evidence.
“Yes, he probably directed them,” Mr. Trump said. “But if he didn’t direct them, he knew everything — and you’ll see that,” he went on, adding that documents would be released soon to bolster his charges.
Mr. Obama, whose advisers have dismissed Mr. Trump’s comments as the ludicrous ranting of a president in trouble, issued what amounted to his own one-word rejoinder hours later on Twitter: “Vote,” he wrote.
No evidence has emerged that before the November 2016 election Mr. Obama was involved in the F.B.I. investigation into Mr. Trump’s advisers and any ties to Russian campaign interference, much less that he directed it, although its existence had been reported in the news media. Mr. Obama was told in January 2017 about telephone calls between Mr. Trump’s incoming national security adviser, Michael T. Flynn, and Russia’s ambassador discussing sanctions that the outgoing president had just imposed on Moscow in response to its attempted election sabotage.
Documents released by Mr. Trump’s allies this week show that several Obama administration officials, including Mr. Biden, requested the identity of the American who was originally unnamed in intelligence reports about contacts with Russia, an American who turned out to be Mr. Flynn. Such “unmasking” requests are made thousands of times a year and, according to the documents, these were approved under normal procedures and the recipients were authorized to receive the information.
But Mr. Trump’s allies suggest the requests indicated that Mr. Obama’s aides must have been involved in trying to “set up” Mr. Flynn, who was interviewed by F.B.I. agents after Mr. Obama left office and eventually pleaded guilty to lying to them. Attorney General William P. Barr last week moved to throw the case out, concluding that the F.B.I. had no basis to interview Mr. Flynn, a decision that Mr. Obama later said undermined the rule of law.
Mr. Trump’s attacks have been amplified by Fox News, other conservative media and his re-election apparatus. He has even used his government platform to advance the charges, posting a campaign-style “Obamagate” video on the official White House Facebook page, an overtly partisan message that would have been seen as crossing a line in past administrations.
Mr. Trump has often aired grievances against political opponents with sensational but unspecific accusations, leaving advisers to follow and try to fill in the lines. In this case, Mr. Trump hopes enough information will be released by his intelligence appointees to muddy the waters and lend a patina of confusion about what Mr. Obama may have done, according to people familiar with his thinking.
Other presidents have feuded with predecessors over policy or politics, even publicly quarreling at times. But putting aside Richard M. Nixon and Watergate, no sitting president in modern times has explicitly and aggressively accused a former president of criminality.
“What makes Trump’s attacks so egregious in contrast to his predecessors is how he simply concocts scandals out of thin air, cooking up conspiracies that have no relation to historical fact,” said Matthew Dallek, a presidential historian at George Washington University.
Mr. Trump turned back to Mr. Obama in March 2017, two days after Jeff Sessions, then the attorney general, recused himself from the investigation into Russian election interference, a move that infuriated the president and led to the appointment of Mr. Mueller.
The president lashed out again last weekend after news reports about Mr. Obama’s criticism of Mr. Barr’s decision to negate Mr. Flynn’s guilty plea.
Mr. Trump began using the term “Obamagate” on Sunday but refused to explain what specific crime he was alleging when asked the next day by a Washington Post reporter. “You know what the crime is,” the president said testily. “The crime is very obvious to everybody. All you have to do is read the newspapers, except yours.”
He still has not explained, but on Thursday morning, he prodded Senator Lindsey Graham, Republican of South Carolina and the chairman of the Senate Judiciary Committee, into opening an investigation.
“If I were a Senator or Congressman, the first person I would call to testify about the biggest political crime and scandal in the history of the USA, by FAR, is former President Obama,” Mr. Trump wrote on Twitter. “He knew EVERYTHING. Do it @LindseyGrahamSC, just do it. No more Mr. Nice Guy. No more talk!”
Less than two hours later, Mr. Graham announced hearings into the Flynn case and other matters, including whether Mr. Mueller should have been appointed in the first place. Mr. Mueller’s investigation concluded that Russia mounted a major operation to tilt the 2016 election to Mr. Trump and that there were multiple contacts with Mr. Trump’s associates, but it did not find enough evidence to charge a criminal conspiracy.
“To say we are living in unusual times is an understatement,” Mr. Graham said in a statement. “We have the sitting president (Trump) accusing the former president (Obama) of being part of a treasonous conspiracy to undermine his presidency. We have the former president suggesting the current president is destroying the rule of law by dismissing the General Flynn case.”
Still, Mr. Graham threw cold water on the idea of calling Mr. Obama. “Both presidents,” he added, “are welcome to come before the committee and share their concerns about each other. If nothing else it would make for great television. However, I have great doubts about whether it would be wise for the country.”
The F.B.I. opened its investigation into ties between Russia and the Trump campaign in July 2016 not long after WikiLeaks released thousands of internal Democratic Party emails that intelligence officials believed had been hacked by Russian intelligence operatives. The investigation, code named Crossfire Hurricane, was handled by a small group of law enforcement and intelligence officials, who did not brief White House officials about the inquiry, according to accounts that have emerged since.
When Mr. Obama and Mr. Trump met in person two days after the November election, Mr. Obama warned him about Mr. Flynn, who had served as the Defense Intelligence Agency director during the Obama administration. Former officials said that the warning concerned Mr. Flynn’s job performance and penchant for conspiracy theories, not any government investigation.
During a search, intelligence officials came across records of the phone calls between Mr. Flynn and the ambassador, Sergey I. Kislyak, that had been intercepted as part of the intelligence agencies’ regular surveillance of Russian officials. In one of the calls, Mr. Flynn had urged Russia not to retaliate for the sanctions as a new, outwardly friendlier administration prepared to assume office.
During a Jan. 5 conversation in the Oval Office that included Mr. Biden; James B. Comey, the F.B.I. director; Sally Yates, the deputy attorney general; and Susan Rice, the national security adviser, Mr. Obama said any law enforcement issues should be handled “by the book,” but he wanted to know as a matter of counterintelligence policy whether he should share sensitive information on Russia with the incoming Trump team, according to a memo by Ms. Rice. During the meeting, he told Ms. Yates that he “did not want any additional information on the matter” regarding law enforcement, according to a recently disclosed F.B.I. summary of an interview with Ms. Yates.
Four days after Mr. Obama left office, Mr. Comey sent F.B.I. agents to interview Mr. Flynn about the calls with Mr. Kislyak. Mr. Flynn’s answers led to him being charged with lying to investigators, which he pleaded guilty to. He later tried to change his plea and Mr. Barr concurred. An apparently skeptical judge will decide whether to allow it.
Maggie Haberman contributed reporting from New York, and Mark Mazzetti and Adam Goldman from Washington.