"The problem for Comey is that both Democrats and Republicans have spent nearly a year attacking him for failing to exercise professional discretion when it mattered, and politicizing the FBI as a result. So whether his testimony will have any sway depends on whether he can overcome his massive credibility problem."
http://theweek.com/articles/703539/james-comeys-credibility-problem
http://theweek.com/articles/703539/james-comeys-credibility-problem