In years past, I would watch McCain at the Munich Security Conference. The experience was never less than bracing. Beside him, others seemed mealy-mouthed. He had known the extremes of human experience, lived in full. His voice contained that fullness. He was a man of conviction. He preferred to be wrong than to bend.

Torture over more than five years of captivity had imbued him with a humanity that transcended politics, even if did not dim his cantankerous bellicosity. He had bombed Vietnam in a losing war of confused aims and official obfuscation. He emerged unbowed in his belief in “the world’s greatest republic, a nation of ideals, not blood and soil,” as he put it in his farewell letter. McCain was obstinate, sometimes to the point of obtuseness.

America’s many failures were as nothing beside American achievement. Stubbornness defined him in an age of finger-to-the-wind opportunism. As a spineless Republican Party folded into the Trump Party, McCain came to stand almost alone as a politician of principle. His party moved. He did not.

Nowhere was McCain greater than on the subject of torture, a practice for which Trump’s sympathies are evident, and not only in his appointment of Gina Haspel — a woman deeply involved in the Bush administration’s “enhanced interrogation” regime — to head the C.I.A. Here is McCain in 2014, responding to the Senate Intelligence Committee Report on C.I.A. methods deployed in the aftermath of the 9/11 attacks:

“I know from personal experience that the abuse of prisoners will produce more bad than good intelligence. I know that victims of torture will offer intentionally misleading information if they think their captors will believe it. I know they will say whatever they think their torturers want them to say if they believe it will stop their suffering. Most of all, I know the use of torture compromises that which most distinguishes us from our enemies, our belief that all people, even captured enemies, possess basic human rights, which are protected by international conventions the U.S. not only joined, but for the most part authored.”

An important voice for “basic human rights” is gone. Trump does not know what human rights are. That McCain voice could be erratic or impetuous, but it was never petty.