Four months ago, Senator John McCain said he would support the exchange of five hard-core Taliban leaders for the release of Sgt. Bowe Bergdahl. “I would support,” he told CNN. “Obviously I’d have to know the details, but I would support ways of bringing him home and if exchange was one of them I think that would be something I think we should seriously consider.”

But the instant the Obama administration actually made that trade, Mr. McCain, as he has so often in the past, switched positions for maximum political advantage. “I would not have made this deal,” he said a few days ago. Suddenly the prisoner exchange is “troubling” and “poses a great threat” to service members. Hearings must be held, he said, and sharp questions asked.

This hypocrisy now pervades the Republican Party and the conservative movement, and has even infected several fearful Democrats. When they could use Sergeant Bergdahl’s captivity as a cudgel against the administration, they eagerly did so, loudly and in great numbers. And the moment they could use his release to make President Obama look weak on terrorism or simply incompetent, they reversed direction without a moment’s hesitation to jump aboard the new bandwagon.

The last few days have made clearer than ever that there is no action the Obama administration can take — not even the release of a possibly troubled American soldier from captivity — that cannot be used for political purposes by his opponents.