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'.
(..) Come sit. Let us talk together now- very simply-as men. Maximus... talk. Five thousand of my men are out there in the freezing mud. Three thousand of them are bloodied and cleaved. Two thousand will never leave this place. I will not believe that they (..)2000 Gladiator