Congressional Polarization (IMAGE) Michigan State University Caption "The partisanship of the largest coalition in the (A) US House of representatives and (B) US Senate, from the session starting in 1979 to the session starting in 2015. Until the late 1990s, bipartisan coalitions were common, but during the 21st century coalitions have been almost entirely partisan." Credit Z. Neal, Michigan State University; S. Aref, Max Planck Institute for Demographic Research Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.