Justice Antonin Scalia on Wednesday called Kennedy's analysis in the DOMA case "jaw dropping" and an assertion of "judicial supremacy" that "envisions the Supreme Court standing (or rather enthroned) at the apex of government."
And this from a close friend -- Scalia and Kennedy joined the court a year apart, were born the same year, and live on the same street.
The Sacramento, California, native joined the high court in 1988, the third choice of President Reagan after more conservative nominees Robert Bork and Douglas Ginsburg flamed out.
And along with O'Connor for almost two decades, the two native Westerners carved out a jumpy place in the center. Less driven by practical concerns than O'Connor was, Kennedy has striven for a loftier sense of the law's impact on society.
"He has brought to the bench a combination of a very scholarly, erudite, academic bent," said Brad Berenson, a friend and former law clerk to Kennedy, "and a very practical bent he had developed while practicing law on his own."
Kennedy himself acknowledged the unique role he played for decades on the court. "There is a loneliness" to his job, he once told CNN.
For now, Kennedy, like his eight colleagues, will retreat from the public spotlight. He has some vacation time ahead, mixed with his annual overseas teaching gig in Austria in two weeks.
Then, come the first Monday October, Kennedy is expected back in his familiar seat, just to the left of Chief Justice John Roberts on the bench. But clearly he is the man in the middle, and the man that in many ways shapes the direction of a divided court.