The Democratic Party achieved a dramatic drop in black voting across the South, with related weakening of the Republican Party in the region. White Democrats were successful in establishing and maintaining a one-party system in most southern states. They thus developed great power in Congress, controlling all seats allocated to their states, establishing seniority, and gaining critical chairmanships of important committees, which extended their power. Black citizens excluded from voting were also shut out of running for local offices, serving on juries, or in other civil offices, and were forced into second-class status.