The chamber was decided Saturday evening after Nevada Sen. Catherine Cortez Masto defeated Republican nominee Adam Laxalt. That gives Democrats 50 seats.
NPR's Michel Martin speaks with Linda Chavez, former White House official in the Reagan administration, about what the midterm results say about the challenges ahead for the Republican party.
Sen. Mark Kelly gave Democrats some breathing room when he clinched his victory in the Arizona Senate race. But open seats leave questions about what the makeup of Congress will look like in January.