Did McCain ad lift 'cross in the dirt' story from Russian novelist?

Senator John McCain (R-AZ), in a Christmas-themed December ad for his presidential campaign, told the following story:

"One night, after being mistreated as a POW, a guard loosened the ropes binding me, easing my pain. On Christmas, that same guard approached me, and without saying a word, he drew a cross in the sand. We stood, wordlessly, looking at the cross, remembering the true light of Christmas. I'll never forget that no matter where you are, no matter how difficult the circumstances, there will always be someone who will pick you up."

"It just sounded so fake and so contrived, so I did a little research about it," said DailyKos contributor rickrocket. The research revealed a similar story by recently departed novelist and McCain favorite Aleksandr Solzhenitsyn, recounting his experience in a Soviet gulag in The Gulag Archipelago, released in the United States in 1973. Luke Veronis, in The Sign of the Cross, recounts:

"Along with other prisoners, he worked in the fields day after day, in rain and sun, during summer and winter. His life appeared to be nothing more than backbreaking labor and slow starvation. The intense suffering reduced him to a state of despair.

On one particular day, the hopelessness of his situation became too much for him. He saw no reason to continue his struggle, no reason to keep on living. His life made no difference in the world. So he gave up.

Leaving his shovel on the ground, he slowly walked to a crude bench and sat down. He knew that at any moment a guard would order him to stand up, and when he failed to respond, the guard would beat him to death, probably with his own shovel. He had seen it happen to other prisoners.

As he waited, head down, he felt a presence. Slowly he looked up and saw a skinny old prisoner squat down beside him. The man said nothing. Instead, he used a stick to trace in the dirt the sign of the Cross. The man then got back up and returned to his work.

As Solzhenitsyn stared at the Cross drawn in the dirt his entire perspective changed. He knew he was only one man against the all-powerful Soviet empire. Yet he knew there was something greater than the evil he saw in the prison camp, something greater than the Soviet Union. He knew that hope for all people was represented by that simple Cross. Through the power of the Cross, anything was possible.

Solzhenitsyn slowly rose to his feet, picked up his shovel, and went back to work. Outwardly, nothing had changed. Inside, he had received hope."

Senator McCain's ad, as posted to YouTube by his campaign on December 20, 2007, is embedded below.