Soon after that campaign, Gregg founded Decima Research, a joint polling/public relations firm. The company became the Conservative party's polling firm, and Gregg played an important role in the 1984 election when the PC Party was led by Brian Mulroney. With the Conservative victory, Decima Research and Gregg entered the halls of power, and he was frequently at Prime Minister Mulroney's side. Decima and Gregg worked for the federal Tories, operated in many provincial elections, and expanded worldwide, participating in over forty-five elections on three continents.