Union backing has been a pivotal piece of the campaign, as Sanders works to define himself as a messenger of the working-class message.

's campaign is out with a new online video touting her support from labor unions just days before her pivotal matchup within the Iowa caucuses.

The ad begins with a Clinton quote splashed across the screen as it shows people representing the labor unions who have flocked to her.

"If anyone asks you if labor will have a seat at the table in my White House, I hope you know the answer. Of course you will, labor built the table," the quote reads.

"A lot of the work you do may not be as well understood and appreciated as it should be," the former secretary of State says in footage from a campaign rally included in the video.

"I know what you are doing and I know hard you are fighting for your members to have a decent standard of living. I will be a president who will stand up for you and fight for you too."

The online video's release comes as the Democratic campaigns make their final push on all fronts before the Iowa caucuses. Her campaign also released two television ads across the state that took a swipe at Sanders's ideas for being too idealistic

Clinton has won the lion's share of union endorsements, a total of 23 national labor unions or alliances compared to five for the Vermont senator. A Clinton campaign aide told The Hill that her labor endorsements include groups representing 13 million people.