I agree with HK2004. There are a number of good policy-oriented PhD programs in the U.S. that might be worth looking at (Georgetown's PhD in poli-sci is not one of them though). JHU-SAIS, Tufts-Fletcher School, Harvard-Kennedy School, Princeton-Woodrow Wilson, U Pittsburgh-GSPIA are all places that has policy oriented PhD programs. There are also other schools that are more leaning toward Public Policy like RAND-Pardee but I don't know if that kind of a route is how you'd like to proceed. It might also be a good idea to check out the Professional Programs - Government Affairs forums, since such programs kind of fall into their jurisdiction.