Over the course of a long and distinguished career, Sen. Edward Kennedy, who died Tuesday at the age of 77, was like a cat with nine lives who used every one of them. He came from a family touched by greatness, even as it was riddled with unfathomable tragedy. He was the torchbearer for liberalism, even when it was a fading voice on the political scene.

If his life was the stuff of rich biography—his memoir, for which he was reportedly paid $8 million, is due out in just over two weeks—the question remains: What will history think of him? Despite all the encomiums, it is too early to tell.

Surveying his impressive 47-year career as one of the lions of the Senate, it is hard not to recall the Senate's "Golden Age," an age before the Civil War when senators...