The most closely watched races is pennsylvania's senate contest. >> it is a big one, and republican mehmet oz has narrowed democrat john fetterman's lead in a tight race that could determine which party controls the senate. cnn's dan merica was at an event for fetterman and joins us now. >> reporter: that's right. john fetterman held an event here in key chester county on saturday night. he spoke at length on stage with senator amy klobuchar. it is a unique event for fetterman, as you noted, had a stroke in may, returned to the campaign trail in june, has mostly headlined rallies where he had ...