McCaskill is running for re-election this year in Missouri, a state Trump won by nearly 20 percentage points. But it's not the first time McCaskill has been critical of her Republican counterpart. The former Missouri prosecutor also criticized Johnson recently for raising the specter of a "secret society" at the FBI plotting against President Donald Trump. Johnson later conceded the "secret society" reference may have been a joke between the two FBI agents.
"If the committee has any evidence that the FBI is, as you have stated, biased and corrupt at the highest levels, I assume that evidence is strong in both quality and quantity, and extends far beyond a casual mention in a text message between two agents who were involved in personal crosstalk," McCaskill wrote to Johnson.
Johnson previously wrote to FBI Director Christopher Wray on Jan. 20 requesting information on missing text messages between Strzok and Page, and how the FBI oversees private accounts for official business.
Strzok, a counterintelligence agent who worked the Clinton email case, last summer was taken off the FBI team investigating whether there are ties between Russia and Trump's presidential campaign after text messages surfaced between Strzok and Page that were derogatory of Trump.
Page had left special counsel Robert Mueller's team before the text messages were found.
The request for new documents comes as Johnson and the House Judiciary and Oversight and Government Reform committees have launched inquiries into the FBI's handling of the investigation into Clinton's use of a private email server as secretary of state, including why Comey did not recommend criminal charges against Clinton.
Democrats have accused Republicans of mounting the investigations with the aim of raising doubt about the FBI's impartiality and deflecting attention from the special counsel's probe into whether Trump's campaign conspired with Russia.
The FBI's performance is also the subject of an independent investigation by the Justice Department's internal watchdog agency, which began looking into it in January 2017.
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