李承乾
By this point, Li Tai, who was considered intelligent and talented in literature, had gained Emperor Taizong's favor over Li Chengqian—so much so that in 638, Emperor Taizong let it slip out that it was not impossible that an imperial prince would one day be his officials' overlord, when Wang Gui suggested that high level officials not be required to bow to imperial princes other than the crown prince. Li Chengqian, meanwhile, was allowing his games to interfere with his studies, despite urgings of his advisor Zhang Xuansu (張玄素). At one point, after Zhang expressed disapproval of his playing drums, Li Chengqian destroyed his drums, but was not otherwise listening to Zhang's advice.