Bernie Sanders's presidential campaign has unveiled a plan to strengthen unions, with the goal of doubling union membership in his first term as president. The plan was released shortly before Sanders was set to speak at the AFL-CIO convention in Iowa.

As with his presidential bid in 2016, Sanders has premised his campaign on supporting and uplifting working-class Americans. Sanders's "Workplace Democracy Plan" includes a provision to end "right to work" laws in several states, which prohibit workers from collective bargaining. The provision would also give every American union worker the right to strike and ban the replacement of striking workers. It's unclear how this provision would be accomplished.

The plan also includes an executive order preventing large companies which engage in union-busting practices from receiving federal funding.

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"Corporate America and the billionaire class have been waging a 40-year war against the trade union movement in America that has caused devastating harm to the middle class in terms of lower wages, fewer benefits and frozen pensions," Sanders said in a statement. "That war will come to an end when I am president."

Other provisions in the plan include requiring companies that merge to honor existing union contracts, stopping corporations from forcing workers to attend mandatory anti-union meetings, and establishing federal protections against the firing of workers for any reason other than "just cause."

Sanders has been a leader in fundraising and has consistently been at the top of polls. However, the latest poll of Democratic Iowa voters by Monmouth University found that Sanders was slipping in the state, as he garnered only 9% support compared to 16% in April.