What preserves the integrity of the Nobel Prize?

I'm not trying to imply that the Nobel Prize doesn't have integrity, but what exactly preserves its integrity? What keeps the Nobel Prize from devolving into some illegitimate award that's based entirely on politics?|||Are you just being facetious or is it that you have not been paying attention. What ever integrity the Nobel Prize ever had has long ago been sacrificed on the the alter of leftist thinking.