Voters report in the LA Times that city police and elected officials in Bell (CA) came and had them sign absentee ballot forms but never asked them to vote the ballot itself.  Among the allegations that city elected officials participated in this activity, and city police officers:

"A 42-year-old Bell woman, who asked to remain anonymous, told The Times that a Bell police officer and two other people came to her door in 2007 before a City Council election. The officer, she said, told her she should support Hernandez and Councilman Victor Bello and asked her to sign a form. She agreed to sign even though she said she was not sure exactly what the form said.

A few weeks later, when she and her husband went to cast their ballots on election day, poll workers told her she had already voted absentee. The poll worker told her the vote could be canceled, and she voted again."