If that's the case, why has neither Trump nor the White House made that clear before now as this allegation has festered?
Most reports focused on the fact that Trump had cited no evidence to back up this charge.
The FBI was looking for evidence that Manafort had maintained a secret offshore bank account - possibly to obtain money from Russian operatives. Lindsey Graham said that if true, Trump's wiretapping claims would be the "biggest political scandal since Watergate".
If true, the new findings would not only mean the Obama administration spied on the Trump Team during the elections, but would also mean that key Obama officials may have lied on record.
It does not seem that Manafort was wiretapped while he served as Trump's campaign chairman. "The special counsel even took the unusual step of obtaining a subpoena for one of Mr. Manafort's former lawyers, claiming an exception to the rule that shields attorney-client discussions from scrutiny".
Former FBI agent Asha Rangappa, who served in the bureau's counterintelligence division, explained earlier this year the FBI can request and be granted a warrant to monitor a USA person from the Foreign Intelligence Surveillance Court "if they can show probable cause that the target is an "agent of a foreign power" who is 'knowingly engag [ing]...in clandestine intelligence activities'". Federal Bureau of Investigation agents raided the Alexandria residence in July. That warrant involved the bureau's investigation into suspected collision between Trump's campaign and the Russian government.
The FBI also eavesdropped on Carter Page, a campaign associate that then candidate Trump once identified as a national security adviser.
"The tactic that Mueller is using - telling Manafort that he will be charged - is generally used when prosecutors are trying to get a defendant to 'flip, '" said Mariotti.
Maddow asked if reports that Mueller has warned Manafort to expect an indictment is more of a "threat or a promise". Steele had reportedly provided copies of reports in the dossier to Federal Bureau of Investigation agents he knew from previous spy projects. "They even photographed the expensive suits in his closet".
The reported surveillance, granted under a court warrant, occurred both before and after the 2016 election.
This second warrant covered an unspecified time leading into early this year.