Daniszewski's journalism career began in 1977 as an Associated Press stringer at the U.S. District Court in Philadelphia while still a student at the University of Pennsylvania. He joined the AP's Philadelphia bureau full-time in 1979, and transferred to the statehouse bureau in Harrisburg in 1980. He reported on the murder of mobster Angelo Bruno, Three Mile Island nuclear accident, the 1980 Pennsylvania Lottery scandal, the Centralia mine fire, the Mariel boatlift, and the campaigns of Arlen Specter and Jim Heinz. He also participated in covering the 1980 Olympics in Moscow, which were boycotted by the United States.