Clayton Kelly, who was arrested late Friday, is being held in lieu of $100,000 bail on a charge of exploiting a vulnerable adult. A judge refused Sunday to reduce the bail.
Kelly has a blog, "Constitutional Clayton," where he has published items supporting state Sen. Chris McDaniel. McDaniel is challenging Cochran, a senator since 1978, in the Republican primary.
Pictures of Rose Cochran appeared on the blog. The video of the photographs was quickly removed.
Kelly was apparently trying to build a case that Cochran had an inappropriate relationship with Kay Webber, his longtime aide.
The right-wing news site Breitbart.com reported Sunday that McDaniel's campaign knew of the video in late April. After Kelly's arrest, the campaign said it knew nothing of the videotape.
Breitbart published an email it said was sent to campaign staff from McDaniel's campaign manager, state Sen. Melanie Sojourner: "Someone has created a video about Thad and Kay. It must come down ASAP. Does anyone know where this came from?"
A Madison police department spokesperson said that others "might have been part of a conspiracy," and that detectives were trying to interview possible co-conspirators.
McDaniel is running as a Tea Party supporter and has received some high-profile endorsements from the Club for Growth and former Alaska Gov. Sarah Palin.