Under Patel, F.B.I. Scours Its Records to Discredit Trump Opponents

As the F.B.I. has added payback to its portfolio, Republican lawmakers like Senator Charles E. Grassley have emerged as a clearinghouse for leaks and whistle-blowers.Under Kash Patel, F.B.I. personnel have worked to paint a damning, one-sided narrative intended to discredit and embarrass federal law enforcement officials who investigated Donald J. Trump and his allies.