Clinton secures another union endorsement, bringing total to 16

The insulators union has endorsed U.S. presidential candidate Hillary Clinton, raising the Democratic front-runner's tally of national labor endorsements to 16 unions representing 11 million workers. 

International Heat and Frost Insulators and Allied Workers President James McCourt said in a letter to Clinton, reviewed by Reuters, that the union recognised her "strong support for fundamental labor standards" and "recognition of the significant contributions of our members to energy efficiency." 

Clinton said in a statement to Reuters: "I am honored to receive the endorsement of the Insulators Union, whose leadership in energy efficiency is essential to making America a clean energy superpower." 

She now has the backing of 16 unions that collectively represent some 11 million workers. Roughly 14.6 million workers - about 11.1 percent of the workforce - are union members, according to U.S. government data. 

Some of Clinton's endorsements include influential unions such as the AFSCME, a public employees union with 1.6 million members, and the Service Employees International Union, or SEIU, which has about 2 million members in a variety of professions that range from nursing to janitorial services. 

The 30,000-member insulators union is a member of the AFL-CIO, a federation of 56 labor unions that collectively represent more than 12 million workers. 

The AFL-CIO itself has not yet endorsed a candidate and has not traditionally done so in recent presidential elections until the party-nominating contests are nearly decided. 

Endorsements by national unions do not prevent their rank-and-file members from supporting a different candidate, such as Clinton's chief rival for the Democratic presidential nomination,...