ใครคือผู้สมัครในเขตที่มีผู้ดำรงตำแหน่งคือ Joe Waggonner?
Who were the candidates in the district whose incumbent is Joe Waggonner?
df = pd.DataFrame(columns=['candidates', 'incumbent'])
df[df['incumbent'] == 'Joe Waggonner']['candidates'].values[0]