The FBI knew full well before it applied for the FISA court warrant on Carter Page that its evidentiary basis—the Christopher Steel dossier on Donald Trump—was opposition research funded by the Clinton campaign. From John Solomon at thehill.com:
When the annals of mistakes and abuses in the FBI’s Russia investigation are finally written, Bruce Ohr almost certainly will be the No. 1 witness, according to my sources.
The then-senior Department of Justice (DOJ) official briefed both senior FBI and DOJ officials in summer 2016 about Christopher Steele’s Russia dossier, explicitly cautioning that the British intelligence operative’s work was opposition research connected to Hillary Clinton’s campaign and might be biased.
Ohr’s briefings, in July and August 2016, included the deputy director of the FBI, a top lawyer for then-Attorney General Loretta Lynch and a Justice official who later would become the top deputy to special counsel Robert Mueller.
At the time, Ohr was the associate deputy attorney general. Yet his warnings about political bias were pointedly omitted weeks later from the Foreign Intelligence Surveillance Act (FISA) warrant that the FBI obtained from a federal court, granting it permission to spy on whether the Trump campaign was colluding with Russia to hijack the 2016 presidential election.