President Trump on Sunday slammed Andrew McCabe in a tweet.

Using a quote from Fox News, President Trump on Sunday continued his attack on FBI Deputy Director Andrew McCabe.
"@FoxNews-FBI's Andrew McCabe, 'in addition to his wife getting all of this money from M (Clinton Puppet), he was using, allegedly, his FBI Official Email Account to promote her campaign. You obviously cannot do this. These were the people who were investigating Hillary Clinton,'" Trump wrote on Twitter.
The president had slammed McCabe on Saturday as well.
"How can FBI Deputy Director Andrew McCabe, the man in charge, along with leakin' James Comey, of the Phony Hillary Clinton investigation (including her 33,000 illegally deleted emails) be given $700,000 for wife's campaign by Clinton Puppets during investigation?" Trump tweeted. "FBI Deputy Director Andrew McCabe is racing the clock to retire with full benefits. 90 days to go?!!!"
McCabe has been repeatedly criticized by Trump and congressional Republicans in the recent past.
As the Washington Post explains, "[McCabe] holds a unique position in the political firestorm surrounding the FBI. He was former director James B. Comey's right-hand man, a position that involved him in most of the FBI's actions that vex President Trump and in the investigation of Hillary Clinton's use of a private email server while secretary of state."
And another catalyst for Trump's attack may have been McCabe's recent testimony in which he reportedly told congressional investigators that Comey had mentioned to him Trump's request for loyalty. 
Many intelligence officials have expressed their growing concern over Trump's attacks on the FBI.
"Trump is attacking senior FBI officials at a time when the bureau is working hand-in-hand with Robert Mueller, a former FBI director, on the Russia probe," Axios notes.