Something from history or politics, where someone thinks their 'supporters' are putting them forward because they want them to be their leader, but really they are only doing it for themselves, and will drop the front man when they get their wish. Any ideas?
Such a person is often called a cat's-paw, based on the fable of the monkey who used a cat's paw to pull chestnuts out of the fire. In politics, a word sometimes used is stalking-horse, since - when stalking deer- the animals are not 'spooked' by a horse and, by hiding behind it, the hunters can get closer to their prey. Mind you, in the latter case, the supposed rival candidate is usually aware that he is being so used.