The nominations are quite a effective process given we get around 50% of the incumbents lose in the nominations.
Take Busia, even the money and closeness to Raila can't even save docile Ojaamong. Unless you buy out key and well organized challengers early enough or use serious threats, you can't be sure.
The party dons need to invest at least half of collections from aspirants to make the nominations even better, though this is against their interests where they have preferred candidates.