The candidates started 'slinging mud' (at each other) early in the campaign.
His shoes were covered with 'mud'. = His shoes were caked in/with 'mud'.
The scandal ruined his reputation and now 'his name is mud'.
(..) before summer's over. Come here! - Hyah, hyah! Vaes Dothrak - the city of the horselords. A pile of mud. Mud and shit and twigs. - Best these savages can do. - These are my people now. - You shouldn't call them savages. - I'll call them what I like, (..)2011 TvShow: Game of Thrones Title: Cripples, Bastards, and Broken Things Season: 1 Episode 4