By Derrick DePledge
U.S. Sen. Brian Schatz shares the distinction of being the most liberal senator, according to the National Journal's 2013 vote ratings.
The Hawaii Democrat is tied for first with U.S. Sen. Charles Schumer, D-N.Y., and U.S. Sen. Chris Murphy, D-Conn.
U.S. Sen. Mazie Hirono is ranked as the fourth most liberal senator.
Schatz is campaigning as a progressive in his primary against U.S. Rep. Colleen Hanabusa.