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.

Whelan tweeted Friday morning: “I made an appalling and inexcusable mistake of judgment in posting the tweet thread in a way that identified Kavanaugh's Georgetown Prep classmate. I take full responsibility for that mistake, and I deeply apologize for it. I realize that does not undo the mistake.”

Ford claims Kavanaugh sexually assaulted her during the 1980s, pinning her to a bed, groping her and covering her mouth to prevent her from screaming. Kavanaugh has denied the claims. His supporters, walking a cautious path, have suggested another person might have been responsible for the alleged attack. Kavanaugh has agreed to testify next week, and Ford's lawyers at Washington's Katz, Marshall & Banks are negotiating the contours of her potential testimony.

Whelan, a Harvard Law School graduate and a popular conservative voice on judicial nomination matters, came under criticism almost immediately for his tweets. Some observers questioned whether Whelan, who identified a former classmate of Kavanaugh as resembling him, could have committed libel. Ford, through her lawyers, told media outlets Thursday “there is zero chance that I would confuse them.”

Whelan said in a statement Friday morning: “No one urged or in any way asked me to make the apology. It was entirely my decision.” He also said: “I did not work with anyone in the White House or on the judiciary committee in preparing my tweet thread.”

On Sept. 18, Whelan, president of the Ethics and Public Policy Center in Washington and a former clerk to the late Antonin Scalia, predicted on Twitter that Kavanaugh, a week from then, “will have been clearly vindicated on this matter. Specifically, I expect that compelling evidence will show his categorical denial to be truthful.”

Whelan has followed Kavanaugh's nomination from the beginning, including attending President Donald Trump's East Room announcement of the D.C. Circuit judge's nomination in July, and live-tweeting the confirmation hearing.

There was debate on Twitter on Thursday night about whether and how much Republicans on the Senate Judiciary Committee and Trump officials had prior knowledge of Whelan's plan before he executed it on social media.

The Senate Judiciary Committee distanced itself from Whelan's tweets, saying the committee “had no knowledge of involvement” in Whelan's Twitter storm. Whelan said Thursday night in his posts that “I do not state, imply or insinuate” that Kavanaugh's classmate “or anyone else committed the sexual assault that Ford alleges.”

Last year, Whelan co-edited a book of Scalia's speeches and writings titled “Scalia Speaks” along with Scalia's son Christopher. In his postings for the National Review, Whelan is a frequent and unabashed critic of liberal judges and the news media. He writes a regular feature called “This Day in Liberal Judicial Activism.”

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Tony Mauro, C. Ryan Barber and Ellis Kim contributed reporting from Washington.