Labor unions exert influence on political policies primarily through collective bargaining and advocacy. They represent the interests of workers, pushing for better wages, benefits, and working conditions. By mobilizing their members, unions can effectively campaign on political issues, endorsing candidates who support workers' rights and lobbying for legislation favorable to labor. Unions play a critical role in shaping public policy and can sway elections by leveraging their resources and collective power, making them significant players in the political landscape.