My concern: No doubt that we are discussing past ..but within that past, sentence discusses " during .. contended" ..so i thought "has" can suffice because within the sentence we are talking about chances of success of wilson's plan.
Past Perfect: The Past Perfect expresses the idea that something occurred before another action in the past. It can also show that something happened before a specific time in the past. (we need to see everything is Past's context)
I had never seen such a beautiful beach before I went to Kauai.
Had you ever visited the U.S. before your trip in 1992?
Yes, I had been to the U.S. once before in 1988.
Mreover, had means that friends are contending about something happened in past whereas sentence means they are discussing about a present plan. I hope u guys get my point..
Wilson's contemporaries contended in the past, thus you can't use the present perfect for what they contended for. They contended for something done is past.