"To date, we've run a solid grassroots campaign, which has resulted in massive support expressed in thousands of bright yellow 'Dennis!' signs springing up in supporters' front yards, but an aggressive, illegal sign removal operation is being run by the other campaign," Kucinich wrote, as reported by a Cleveland ABC affiliate, Channel 5. 

The TV station reported that a Kucinich spokesman, Andy Juniewicz, explained that the Kucinich campaign possesses proof of the vandalism in the form of license plate numbers and photographs and said that signs were being torn down across Cleveland and in many cases had been replaced with Kaptur signs. 

In a comment to The Hill, however, Juniewicz said the Kucinich campaign was not directly accusing Kaptur of stealing the signs. 

"Our campaign has not directly accused Rep. Kaptur or anyone else of stealing campaign signs. Our campaign sings have been stolen and our campaign has gathered information and referred it to our legal counsel," he said.

Kaptur’s press secretary, Matthew Klempner, issued a flat denial. 

“We are certainly opposed to any theft or destruction of anyone's property, including yard signs,” he said. “We don't engage in such behavior.”

The battle for Ohio's 9th district has drawn national attention because of Kucinich, a liberal icon and former presidential candidate who has received endorsements from Rep. Barney Frank (D-Mass.) and celebrities such as country music star Willie Nelson.

This story was updated at 10:43 a.m.