By Amanda Becker

LOS ANGELES (Reuters) - Democratic presidential candidate Hillary Clinton has hired two people with close ties to U.S. organized labor to try to lock down support from union members as Republican candidate Donald Trump makes courting working-class voters central to his campaign. 

    The two new staffers, Lori D'Orazio and Michele Gilliam, are to be deputy labor campaign directors, according to a campaign aide. D'Orazio is moving to the campaign from the biggest U.S. labor federation, the AFL-CIO. Gilliam is a former staffer for Senator Bernie Sanders of Vermont, who was Clinton's fiercest primary competitor.

    Clinton and Sanders battled fiercely over union support during the Democratic primary, with Clinton, the presumptive nominee, ultimately securing the bulk of the national endorsements from labor unions. But she will need to harness the on-the-ground manpower of unions in crucial battleground states ahead of November's general election match-up with the populist presumptive Republican nominee, Trump. The aide said the campaign is counting on D'Orazio and Gilliam to do just that.

Although organized labor is a traditionally Democratic constituency, Trump has made a play to win over rank-and-file union members by criticizing international trade deals such as the pending Trans Pacific Partnership, which labor opposes. Even so, AFL-CIO President Richard Trumka warned last month when the federation endorsed Clinton that a Trump presidency would be disastrous for U.S. workers and vowed to mobilize the group's resources to defeat him. 

The AFL-CIO is the largest U.S. federation of labor unions that collectively represent more than 12 million workers. Before joining the AFL-CIO, D'Orazio worked for another large U.S. union, the United Auto Workers, and Gilliam once served as an organizer for a local chapter of the Transport Workers Union.

(Reporting By Amanda Becker; Writing By Emily Flitter; Editing by Dan Grebler)