District Attorney Brian Blanchard will be allowed to continue as prosecutor in the John Doe investigation into allegations that caucus workers illegally campaigned on state time.

Dane County circuit judge Sarah O’Brien made the ruling Wednesday after a 5-hour hearing in which she listened to evidence that, during his 2000 campaign, Blanchard may have benefited from a relationship between caucus workers and campaign volunteers.

O’Brien heard testimony from 12 witnesses, including five former employees of the Senate and Assembly Democratic caucuses, Blanchard and two former members of Blanchard’s campaign.

Milwaukee County District Attorney E. Michael McCann, who has been working with Blanchard on the case for the past year, testified that during his investigation into the allegations, he saw there was no reason Blanchard could not continue with the investigation.

Blanchard and McCann will continue to investigate three partisan caucuses.

“A full airing has taken place, and it is clear that there is neither an actual nor perceived conflict of interest in Blanchard continuing his role as prosecutor in this action,” O’Brien wrote in her decision. “He has been elected to enforce the laws in this jurisdiction and should continue to do so without restrictions.”

Common Cause of Wisconsin said efforts to halt the investigation have failed.

“It appears that the best efforts of Sen. Brian Burke, D-Milwaukee ? [ and] other legislators under criminal investigation and those who are trying to maintain the corrupt status quo in Madison, to smear and undermine the credibility of the lead prosecutor in the 15-month old legislative caucus scandal investigation — Dane County District Attorney Brian Blanchard — have failed miserably,” said Jay Heck, executive director.