A friend of Christine Blasey Ford told FBI investigators that she felt pressured by Dr. Ford’s allies to revisit her initial statement that she knew nothing about an alleged sexual assault by a teenage Brett Kavanaugh, which she later updated to say that she believed but couldn’t corroborate Dr. Ford’s account, according to people familiar with the matter.

Leland Keyser, who Dr. Ford has said was present at the gathering where she was allegedly assaulted in the 1980s, told investigators that Monica McLean, a retired Federal...