Beijing also strengthened the Liaison Office to influence day-to-day affairs in Hong Kong and effectively operated as a "second government" in Hong Kong, reviewing and approving all potential candidates in the elections. Cao Erbao, director of the Liaison Office's Research Department who coined the "second government" concept, wrote that Hong Kong went from being ruled by one entity to being ruled by two: the Hong Kong government and "a team of Central and Mainland authorities carrying out Hong Kong work." It sparked great controversy in some sectors of Hong Kong society, already worried about the growing interference of the People's Republic of China into Hong Kong's political affairs. Since 2010, Hong Kong protesters began targeting the Liaison Office as the destination of the demonstrations.