According to the 2015 Bipartisan Index
Two 2016 presidential hopefuls are also the top two most partisan people in the Senate, according to new data.
The Lugar Center and Georgetown University’s McCourt School of Public Policy published their 2015 Bipartisan Index on Monday, which measures how often each member of Congress co-sponsored a bill introduced by someone from their opposing party or attracted co-sponsors for their own bills from the opposite party. By this standard, in 2015, Bernie Sanders ranked as the most partisan person on the Senate side, and Ted Cruz ranked as the second-most partisan. Though Sanders is an Independent in the Senate, he was counted as a Democrat.
Sens. Susan Collins and Joe Donnelly were the top ranked bipartisan Senators, reaching across the aisle the most frequently. Majority Leader Mitch McConnell and Minority Leader Harry Reid were not included in the ranking.
Looking at lifetime scores rather than just the 2015 data, Sanders and Cruz are not at the very bottom of the Senate list, but they still rank quite low for bipartisanship.