Voters in states where Donald Trump plans to campaign especially hard over the next four months have begun receiving pro-Hillary Clinton mailers, courtesy of the nation's largest union federation.

The AFL-CIO on Wednesday announced its latest direct mail initiative, which will target swing-state voters in Florida, Ohio, Nevada, Pennsylvania and Wisconsin. The group endorsed Clinton in mid-June, shortly after she clinched the Democratic presidential nomination.

"Your union has done the research and recommends Hillary Clinton for president," the mailer reads, before advising union members their "decision [for whom to support] will affect your job and your family."

A fact sheet about Trump that's included in the mailer claims the Republican hopeful "would do without unions altogether ... drive down wages and [take] power away from working people."

Recipients are encouraged to cast their ballots for Clinton, who the AFL-CIO claims is "committed to ensuring new manufacturing, clean energy and transportation jobs" and "believes in the fundamental right of working people to organize ..."

"This piece puts side-by-side the important differences between Hillary Clinton and Donald Trump when it comes to the right to organize," the federation's national media director Josh Goldstein said of the mailer.

Trump's blunt criticism of multinational trade agreements and rejection of traditional politics has been well-received among some unionized workers, so much so that Service Employees International Union president Mary Kay Henry was forced to acknowledge his appeal.

"There is deep economic anxiety among our members and the people we're trying to organize that I believe Donald Trump's message is tapping into," Henry told the New York Times in January, months before Trump became the presumptive GOP presidential nominee.

The AFL-CIO has previously sought to reach union voters who might be sympathetic to Trump with videos highlighting the pending lawsuits against his now-defunct online college and comments he's made about wages in the U.S.