Conservative activist Ed Whelan, under fire for a series of tweets that were designed to boost attacks on the credibility of the woman accusing Brett Kavanaugh of sexual assault, apologized Friday on Twitter for what he called “an appalling and inexcusable” mistake in judgment.

Whelan, who has backed Kavanaugh’s nomination to the U.S. Supreme Court, posted tweets late Thursday that used yearbook photos, housing records and maps to suggest the accuser, California professor Christine Blasey Ford, might be confusing Kavanaugh with another high school classmate at Georgetown Preparatory in suburban Washington. He has since deleted those tweets.