As an AI language model, I do not have access to the latest updates or developments in real-time, and my training data only goes up to September 2021. Therefore, I am not aware of any recent developments regarding the television series "Succession" or the characters involved.

However, based on my knowledge of the show up to September 2021, I cannot provide a specific answer to your question. It is possible that there may not be enough information available to identify the moderate candidate Shiv wants ATN to back or it could be a plot point in a future episode that has not yet been released.