Together, they have pursued cases against the president’s enemies and protesters and amplified false claims of widespread election fraud, often citing thin evidence.
In court testimony, the agent outlined the willingness of Kash Patel, the F.B.I. director, to take orders from President Trump to investigate his perceived enemies.
Lawyers for James B. Comey said the case centered on an issue that had already been investigated and had not led to charges, of a purported leak of national security information to The Times in October 2016.
The charges intensified the administration’s efforts to go after the law enforcement and intelligence personnel who cast doubt on unsubstantiated claims that Joseph R. Biden Jr. engaged in corrupt dealings in Ukraine.