But on Sunday, the president condemned Mr. Comey as a liar, saying that “I never asked Comey to stop investigating Flynn” and that Mr. Comey had harmed the bureau and its employees. He also accused the bureau’s agents of spending years pursing a “phony and dishonest” investigation into the email server of his 2016 rival, Hillary Clinton.
Mr. Trump’s fury at those investigating him stunned even those with fresh memories of his repeated attempts over the past year to disparage intelligence agencies, the State Department and other parts of his government. Senator Dianne Feinstein of California, the top Democrat on the Judiciary Committee, said the frenzied nature of the president’s tweets suggested that he knew that Mr. Mueller was building an obstruction of justice case against him.
“I see it in the hyper-frenetic attitude of the White House, the comments every day, the continual tweets,” Ms. Feinstein said on NBC’s “Meet the Press” on Sunday.
Eric H. Holder Jr., who was President Barack Obama’s first attorney general, responded to the president’s tweets with one of his own defending the bureau. “You’ll find integrity and honesty at FBI headquarters and not at 1600 Penn Ave right now,” Mr. Holder wrote.
As he sought to discredit the Russia inquiry, which he has long called a political “witch hunt,” Mr. Trump on Sunday seized on reports that Mr. Mueller had removed a veteran F.B.I. agent because he sent text messages that appeared to express views critical of Mr. Trump.
In several tweets, the president harshly criticized the agent, Peter Strzok, who had previously helped lead the 2016 investigation into whether Mrs. Clinton had mishandled classified information on her private email account. Mr. Strzok is considered one of the bureau’s most experienced and trusted counterintelligence investigators.
“Report: ‘ANTI-TRUMP FBI AGENT LED CLINTON EMAIL PROBE,’” Mr. Trump said in his 10th tweet on Sunday, which by the early evening had been retweeted more than 24,000 times. “Now it all starts to make sense!”
Most presidents enter the Oval Office with an instinct to defend and promote the integrity and capabilities of the nation’s law enforcement agencies. Mr. Trump arrived with a different compulsion, fueled by a belief that intelligence and law enforcement officials were stoking questions about the legitimacy of his election victory.
By suggesting — as he has before…