'Who can believe this?': Trump rounds on Biden over Flynn 'unmasking'

Former FBI special agent: 'They are unmasked when the identity is necessary to understand the intelligence. All legal, no warrant required.'

Donald Trump joined Senate Republicans in slamming former Obama administration officials, including his presumptive 2020 general election foe Joe Biden, of being involved in a "massive" plot to take him down.

"The unmasking is a massive thing," he said of the former vice president and others in the previous administration seeking to find out who was on the other end of phone calls with Russia's then-ambassador to the United States. It turns out it was Michael Flynn, his 2016 campaign adviser and first national security adviser.

Mr Trump, speaking to reporters at the White House, accused Mr Biden of lying during a television interview earlier this week.

"I was aware that there was, that they had asked for an investigation," Mr Biden told ABC News. "But that's all I know about it."

The president the next day said those two comments do not square.

"He said he knows nothing about anything," Trump said, before saying Biden was an unmasker and questioning why he could say he knew nothing. "He knows nothing about anything. ... And then it gets released today that he's a big unmasker. How do you know nothing if you're one of the unmaskers?"

The latest controversy of the Trump era comes just days after Bill Barr, Mr Trump's hand-picked attorney general, moved to drop all charges against Mr Flynn. The retired Army three-star general had pleaded guilty to lying to the FBI, a plea he has revoked.

Over 15 former Obama administration officials, including Mr Biden, sought the "unmasking" of a person who was on the other end of wiretapped phone calls of then-Russian Ambassador to the US Sergey Kislyak between December 2016 and early January 2017, key Republicans senators announced on Wednesday.

The announcement is part of a larger plan among GOP legislators to lean into Donald Trump's "Obamagate" theory, which maintains that the former president and his top intelligence chiefs sought to entrap incoming Trump officials in legal controversy to kneecap Mr Trump's presidency from the start.

Republican senators like Rand Paul of Kentucky and Ron Johnson of Wisconsin want the former Obama administration officials to, in the latter's words, "confirm whether they reviewed this information, why they asked for it and what they did with it, and answer many other questions that have been raised by recent revelations."

Mr Johnson's statement came as GOP senators are embracing what Mr Trump over the weekend took to Twitter to dub "Obamagate," a rather convoluted conspiracy theory with many tentacles that, essentially, alleges senior Obama administration officials, including Barack Obama and Mr Biden, were part of an effort to sink his 2016 candidacy and then his presidency.

"This is about abuse of power," Mr Paul said Wednesday on Fox News, minutes before Mr Trump spoke to reporters at the White House.

Mr Paul used the term "illegal unmasking" on Fox, and earlier told reporters on Capitol Hill that Mr Biden is "guilty" of using the federal government for political purposes.

But one former law enforcement official contends the former Obama officials did nothing wrong, writing on Twitter they were merely following normal practices.

Identities are masked when a US person who is NOT the target of the surveillance is captured on the communication -- this is an 'incidental communication,'" Asha Rangappa, a former FBI special agent tweeted. "They are unmasked when the identity is necessary to understand the intelligence. All legal, no warrant required."

–Griffin Connolly contributed to this report.