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'.
(..) There they are! Sorry we're late. Somebody took a little convincing. Yup. I really didn't want to come, but Brad insisted. Oh, you big, old, fat stick in the mud! Come on in, you guys. - They're here, everybody! - What's up? - Here you go. Would you like some punch? Is there alcohol in this? (..)2009 TvShow: It's Always Sunny in Philadelphia Title: The Waitress Is Getting Married Season: 5 Episode 5