FILE PHOTO: Democratic 2020 presidential candidate Elizabeth Warren makes one of a series of local visits in Fairfield, Iowa, U.S. May 26, 2019. Picture taken May 26, 2019. REUTERS/Rachel Mummey/File Photo

NEW YORK (Reuters) - Democratic presidential candidate Elizabeth Warren on Thursday endorsed her campaign staff’s decision to unionize, an expected move from the U.S. Senator from Massachusetts who has made workers’ rights a major part of her 2020 platform.

The staunchly pro-labor senator joins three other Democratic presidential candidates - U.S. Senator Bernie Sanders of Vermont, U.S. Representative Eric Swallwell of California and former U.S. housing secretary Julian Castro of Texas - in supporting their respective campaign workers’ decision to join a union.

“My campaign has submitted their support to join @IBEW 2320. Every worker who wants to join a union, bargain collectively, & make their voice heard should have a chance to do so. The labor movement has long fought for the dignity of working people, & we’re proud to be part of it,” Warren tweeted on Thursday.

The campaign workers will be represented by the International Brotherhood of Electrical Workers Local 2320, based in Manchester, New Hampshire.

Warren has built up the largest campaign staff among her 23 other Democratic rivals, spending more than $1 million in the first three months of the year and employing 161 people, according to first-quarter campaign finance reports.