U.S. Rep. Chris Deluzio has held off a challenge from state Rep. Rob Mercuri in the race for Pennsylvania's 17th Congressional District.

A fourth district is in southern Pennsylvania, where Republican Rep. Scott Perry is seeking a seventh term. Another competitive contest was in the suburbs and former steel towns west of Pittsburgh where Democratic Rep. Chris Deluzio won a second term. Here is a look at those five key races:

Democratic U.S. Rep. Chris Deluzio defeated challenger Rob Mercuri, a Republican state representative, in a key congressional district that could be crucial to determining which party controls the U.S.