Cooper worked for Good Schools Pennsylvania, an advocacy organization for public schools.[2] She first began working for Ed Rendell as deputy mayor for Policy and Planning during his tenure as Mayor of Philadelphia.[2][3] When he was elected Governor of Pennsylvania she was appointed Director of the Governor’s Policy Office.[4] In 2004, the office was renamed the Governor’s Office of Policy and Planning and was elevated to a cabinet-level position.[4][5]
In 2003, the political website PoliticsPA named Cooper one of the 50 most powerful individuals in Pennsylvania politics.[6] She was also called one of the "smartest staffers" in 2004 by the same website.[2] She was also named one of the state's "Most Politically Powerful Women."[7]
In a 2009 article, The Philadelphia Inquirer said that Cooper was one of the "chief architects of state policy and a key player behind the crafting of a state budget" and that "she wields tremendous power and is a natural lightning rod for criticism."[3]
In November 2010, Cooper joined the Center for American Progress as a senior policy fellow on their economic policy team.[8]