FILE PHOTO: Democratic 2020 U.S. presidential candidate and U.S. Senator Bernie Sanders (I-VT) speaks at a campaign town hall meeting at La Poste in Perry, Iowa, U.S., January 26, 2020. REUTERS/Ivan Alvarado/File Photo

WASHINGTON (Reuters) - The American Postal Workers Union (APWU) announced on Thursday that its executive board has endorsed U.S. Senator Bernie Sanders to be the Democratic presidential nominee on behalf of its 200,000 members nationwide.

The APWU endorsement comes with Iowa set to host the first nominating contest on Monday. Opinion polls there show Sanders jockeying for first place with former Vice President Joe Biden.

APWU President Mark Dimondstein said the union was pleased that a number of Democrats vying to take on Republican President Donald Trump in November have “taken positions and actions supportive of postal workers and expanding union rights.”

“But when we judge candidates by their long-term and consistent actions, Bernie Sanders stands out as a true champion of postal workers and all workers throughout the country,” he added.

The APWU also endorsed Sanders during his 2016 primary race against Hillary Clinton.

Union endorsements can provide candidates with critical on-the-ground support in key areas as they mobilize workers to knock on doors and man phone banks on behalf of campaigns. Many national unions have thus far remained neutral in the 2020 nominating contests due to the crowded field of Democrats in the race.

Sanders has also received endorsements from National Nurses United and the United Electrical, Radio and Machine Workers of America. The National Union of Healthcare Workers endorsed both Sanders and fellow progressive U.S. Senator Elizabeth Warren.

Biden has been endorsed by the International Association of Bridge, Structural, Ornamental, and Reinforcing Iron Workers; the International Association of Fire Fighters and the National Association of Government Employees.