Anthony Kennedy is a reliably conservative Supreme Court justice, but he’s recently become a bugbear of the right. Tom DeLay called Justice Kennedy’s work “incredibly outrageous” on April 20. Two weeks earlier, at a conference in Washington, D.C., titled “Confronting the Judicial War on Faith,” one speaker called for Justice Kennedy’s impeachment and another essentially advocated his assassination.

Such criticisms of Justice Kennedy are offensive and illogical. They seem aimed at intimidation and wouldn’t be worth mentioning if not for one thing: There’s a historical parallel that shows they could backfire. As New York Times reporter Linda Greenhouse shows in her new biography, “Becoming Justice Blackmun: Harry Blackmun’s Supreme Court Journey” (Times Books, 288 pages, $25), the harsh reaction to former Supreme Court Justice Harry Blackmun’s decision in Roe v. Wade was one key factor that helped to transform him from a moderate conservative into a staunch liberal. Might Justice Kennedy similarly turn around the arrows fired at him?

Appointed to the court in 1970 by Richard Nixon, Blackmun pleased his patron with his early rulings – supporting, for example, the administration’s right to block the publication of the Pentagon Papers. But Blackmun didn’t want to walk a party line when the court was asked to review several state laws that criminally sanctioned doctors who performed abortions.

Though conflicted about the topic, Blackmun had long served as the general counsel for the Mayo Clinic and objected to the idea of states putting handcuffs on doctors. Abortion, he wrote in Roe v. Wade, was “inherently, and primarily, a medical decision, and basic responsibility for it must rest with the physician.”

In his famous decision, Blackmun said nothing about, and seemed wholly uninterested in, the rights of women. But his decision was greeted with intense venom, angry letters, and persistent death threats. This pressure, in turn, sent the justice into a defensive crouch and seemed eventually to turn him into a feminist.

As time passed, Blackmun became a much stronger supporter of abortion rights and adopted the arguments of abortion’s staunchest defenders. On the day he left the Supreme Court, Blackmun defended Roe v. Wade as “a step that had to be taken as we go down the road toward the full emancipation of women.”

The second important story line in Ms. Greenhouse’s book is the friendship between Blackmun and Warren Burger. The two Minnesota natives were best friends from kindergarten until they served on the Supreme Court together. Then what should have been one of the century’s most epic friendships ended in petty sniping.

Burger, nominated to be Chief Justice by Nixon in 1969, was instrumental in bringing Blackmun to the court, but he couldn’t handle Blackmun’s inevitable dissents. Blackmun also quickly lost respect for Burger as a leader and a thinker. Soon the two were sparring over opinions, Blackmun’s clerks were openly dissing the chief, and Blackmun himself was giving off-the-record interviews for “The Brethren,” a book that criticized Burger. They drifted so far apart that, the day before Burger announced his retirement, the two were bickering about footnotes.

As with much else in this book, the story that “Becoming Justice Blackmun” tells about the friendship is fascinating but also incomplete. Blackmun’s papers are fascinating, and Ms. Greenhouse has dug deeply. But the author didn’t take the time to write a true biography: If something wasn’t put on a piece of paper that ended in Blackmun’s files, it’s not in this book. This deprives the reader of much of the most important context for her discoveries.

One victim of this approach is Burger. The book provides a fascinating partial portrait of a man who seemed to lose his grip on life as soon as he had a full grip on power. But we don’t understand why. Burger writes to Blackmun about finding “booby traps” in his early days on the court and scrawls an illegible note asking, “How would you like my job?” in 1974. Yet, as Burger’s notes to Blackmun disappear, his thoughts disappear from the book, as well.

Ultimately, the real victim of this book is Blackmun. Ms. Greenhouse’s title and her conclusion indicate a respect for Blackmun’s transformation into a liberal icon. But Blackmun seems to have been driven to that position in part because of his political reactions, which isn’t the most admirable motivation for someone hired to interpret the Constitution.

Moreover, Blackmun comes across as an intellectual middleweight. He never seems to be an intellectual leader, and his best-known lines weren’t even his. His famous aphorism about affirmative action – “In order to get beyond racism, we must first take account of race” – was essentially stolen from an Atlantic Monthly article. His famous dismissal of the death penalty – “From this day forward, I no longer shall tinker with the machinery of death” – was written by a clerk.

Perhaps that creates one more parallel with Justice Kennedy, a justice often accused of having a confused ideology. If a judge doesn’t have the firmest intellectual bearings, he’s much more likely to blow with the wind. Or, perhaps, to turn his back on the wind if he feels threatened by it.

Mr. Thompson last wrote in these pages on free speech.