The FBI agent removed from special counsel Robert Mueller's probe into possible collusion between the Trump campaign and Russia once referred to President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE as an "idiot" in a text message, according to documents obtained by multiple news outlets.

The agent, Peter Strzok, was removed from his assignment after Mueller learned of the texts, but he then became a target for GOP critics of the probe, who claim it's tainted by bias against Trump.

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Details of the text messages were contained in documents handed over to Congress by the Justice Department late Tuesday.

In one of the 375 disclosed text messages between Strzok and FBI colleague Lisa Page, Strzok said that Sen. Bernie Sanders Bernie SandersButtigieg stands in as Pence for Harris's debate practice Bernie Sanders warns of 'nightmare scenario' if Trump refuses election results Harris joins women's voter mobilization event also featuring Pelosi, Gloria Steinem, Jane Fonda MORE (I-Vt.) was "an idiot like Trump," according to USA Today.

Page also once reportedly referred to Trump as "a loathsome human."

"Yet he may win," Strzok replied, according to USA Today. "Would be a worse president than Cruz?" he asked, referring to Trump's primary challenger Sen. Ted Cruz Rafael (Ted) Edward CruzTrump argues full Supreme Court needed to settle potential election disputes Press: Notorious RBG vs Notorious GOP The Hill's Morning Report - Sponsored by Facebook - Washington on edge amid SCOTUS vacancy MORE (R-Texas.)

Strzok, a top counterintelligence official, also worked previously on the investigation into Hillary Clinton Hillary Diane Rodham ClintonButtigieg stands in as Pence for Harris's debate practice Senate GOP sees early Supreme Court vote as political booster shot Poll: 51 percent of voters want to abolish the electoral college MORE's use of a private email server while secretary of State.

"God, Hillary should win 100,000,000 - 0," Strzok said in one message to Page seen by USA Today.

In another conversation, Strzok suggested the Republican party "needs to pull their head out of their ass."

The Justice Department's inspector general discovered the texts during an assessment into the FBI's handling of the Clinton investigation.

- This story was updated at 10:21 P.M. EST.