From the story here:
Strzok has been a target of withering criticism since text messages he exchanged with FBI lawyer Lisa Page became public. In thousands of messages, Strzok and Page disparage the president and other political figures.
In one exchange, Page asked Strzok: "Trump's not ever going to be president, right? Right?!"
In response, Strzok wrote, "No. No he won't. We'll stop it."
That text exchange was one of 40,000 reviewed by the Justice Department's inspector general in the course of its review of the investigation into former Democratic presidential contender Hillary Clinton's private email server. Strzok played a senior role on the Clinton email investigation.
The inspector general's report, made public in June, found that there was no evidence that Strzok took any action in that inquiry as a result of political bias. The text messages, however, "cast a cloud over the entire FBI investigation," the inspector general concluded.