(CBS) – A North Side political hopeful is in hot water, over a social media post showing the feet of a man sleeping on the L.

AS CBS 2’s Mai Martinez reports, some critics are calling it “homeless shaming.”

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“It was inappropriate,” says Arthur Noah Siegel.

He is talking about his controversial post on Instagram and Facebook last week. It shows someone’s feet in hole-filled socks resting on an L seat. The post describes the feet as “stinky.”

Siegel, who’s running for Illinois state representative against incumbent Kelly Cassidy in the Democratic primary, says he deleted the post after about an hour.

But by then, screen shots were already being shared on social media by people disturbed that someone running for public office would post such a thing.

He indicates the photo was meant to show the reactions of other riders, even though the image is a close-up of the L rider’s feet.

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“I fully take responsibility for it, and you know, it was a mistake post, and it got pulled down. I apologize if anyone was offended over it,” Siegel says.

Rep. Cassidy says she’s not surprised by the backlash.

“That just speaks to what this neighborhood and the values of this neighborhood are. This is an incredibly progressive, thoughtful, inclusive community,” Cassidy says.

Siegel blames his poor judgment on the stress he’s under from challenging Cassidy’s primary petition signatures — and challenges on his own petitions.

To that, Cassidy responded: “If this process is too stressful, the job is even more so.”

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As Siegel works to try to prove fraud on Cassidy’s petitions, he faces his own fight to prove there’s none on his own nominating papers.