Clinton lands another union endorsement
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Hillary ClintonHillary Diane Rodham ClintonRetired lieutenant general tears into Trump over attacks against Navy SEAL: 'Disgusting' Retired admiral who oversaw bin Laden raid doubles down on Trump criticism Trump dismisses criticism from Navy SEAL who led Osama bin Laden mission MORE landed another endorsement from a national union group on Thursday, growing her lead over Democratic presidential rival Sen. Bernie SandersBernard (Bernie) SandersDems wonder if Sherrod Brown could be their magic man My fellow Democrats should watch their language: Economic equality is not a rational societal goal As Democrats gear up to challenge Trump in 2020, the key political divide will be metropolitan versus rural MORE (I-Vt.) in the race for labor support.

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The International Heat & Frost Insulators & Allied Workers, a group that claims 30,000 members, cited Clinton’s support for energy efficiency in its endorsement.

“In addition to your strong support for fundamental labor standards, and your leadership and vision for an American economy that is focused on strong, fair and long-term growth, the Insulators are especially pleased with your recognition of the significant contributions of our members to energy efficiency,” the group said in a letter.

Clinton and Sanders have been battling for labor union support, with the former secretary of State opening up a sizable lead in endorsements.

The Insulators endorsement gives Clinton 16 national labor groups in her corner, including heavyweights such as the Service Employees International Union, the National Education Association and the American Federation of State, County and Municipal Employees.

Sanders has only two national unions backing him — the American Postal Workers Union and National Nurses United.

Still, Sanders has argued that while the unions' corporate boards have voted to support Clinton, many individual members remain in his corner.