A candidate put forward instead of any of several potentially successful candidates in order to initiate a leadership debate, gauge feelings, divide opposition etc
In politics, a stalking horse is someone who stands against a leader in order to see how strong the opposition is. The stalking horse then withdraws in favour of a stronger challenger. The possibility of another stalking horse challenge this autumn cannot be ruled out. someone or something that hides someone's true purpose, especially a politician who says they want their leader's job when the real plan is that another, more important politician should get it
disapproval If you describe a person or thing as a stalking horse, you mean that it is being used to obtain a temporary advantage so that someone can get what they really want. I think the development is a stalking horse for exploitation of the surrounding countryside