The image was posted by the Louisiana politics blog The Hayride in a post with the headline "Mary Voted To Kill The Filibuster Today" — referring to Landrieu joining Democrats in voting to change Senate rules to remove the filibuster option from judicial and executive nominees in the Senate. The photo's title was "MussoLandrieu."
Cassidy's campaign manager, Joel DiGrado, tweeted out the link and the title. He did not respond to repeated inquiries by Politico, which highlighted the tweet.
Landrieu's campaign called for an apology.
"Louisiana politics is colorful and spicy, but this picture is downright despicable and disrespectful," Landrieu campaign manager Adam Sullivan said in a statement on Friday. "Simply tweeting the image was bad enough, but refusing to take it down now is even worse. The Cassidy campaign owes an apology to Sen. Landrieu and should immediately take down this hurtful reminder of one of the worst and most horrific events in world history."
This post has been updated.