To besmirch something or someone is to tarnish their reputation. An example of a sentence using the word "besmirch" is "The editor of the newspaper was persistently attempting to besmirch the mayor. "

besmirch

To stain or dirty, either a persons reputation or a material object. "The allegations he made besmirched her character" "The cloth had been besmirched by mud"

In order to besmirch the reputation of his opponent, Clay made sure to bring up the subject of the senator's tax troubles during their first debate.

Because he does not want to besmirch his name.