CANTON, Mass — National Nurses United, the largest union and professional association of registered nurses in the United States, and its affiliate, the Massachusetts Nurses Association/NNU, announced today its endorsement of Congressman Ed Markey for U.S. Senate in the June 25 Massachusetts special election. “Congressman Markey is a champion of the issues that matter most to nurses: federal and state legislation to require safe RN-to-patient staffing limits for nurses in acute care hospitals, universal single-payer health care, a robust social insurance program and a financial transaction tax on Wall Street trades that would generate hundreds of billions of dollars every year,†said MNA/NNU President, Donna Kelly-Williams, RN.