From the OIG report:
We were deeply troubled by text messages sent by Strzok and Page that potentially indicated or created the appearance that investigative decisions were impacted by bias or improper considerations. Most of the text messages raising such questions pertained to the Russia investigation, which was not a part of this review. Nonetheless, when one senior FBI official, Strzok, who was helping to lead the Russia investigation at the time, conveys in a text message to another senior FBI official, Page, that “we’ll stop” candidate Trump from being elected—after other extensive text messages between the two disparaging candidate Trump—it is not only indicative of a biased state of mind but, even more seriously, implies a willingness to take official action to impact the presidential candidate’s electoral prospects. This is antithetical to the core values of the FBI and the Department of Justice. Moreover, as we describe in Chapter Nine, in assessing Strzok’s decision to prioritize the Russia investigation over following up on the Midyear-related investigative lead discovered on the Weiner laptop in October 2016, these text messages led us to conclude that we did not have confidence that Strzok’s decision was free from bias.