Related Clues:

• Attack ad, maybe
• Slide specimen
• Malign
• Besmirch
• Slight on the stump, say
• Drag through the mud
• Mirror marrer
• Smear on
• Campaign low blow
• Underhanded campaign tactic
• Bad mark
• Window washer's mistake
• Microscope sample
• Spread (on)
• Apply, as plaster or paint