MADISON, Wis. -- A secret investigation into Republican Wisconsin Gov. Scott Walker's former aides and associates closed last week without any charges being filed against Walker.
Milwaukee County District Attorney John Chisholm announced Friday that the so-called John Doe investigation into illegal campaign activity ended on Feb. 20.
The investigation has hounded Walker -- a possible 2016 presidential candidate -- throughout his first two years in office. Walker steadfastly and repeatedly denied he had done anything wrong, even as six people around him were charged with crimes stemming from activity in the Milwaukee County executive's office when Walker held that position.
Walker was county executive for eight years prior to being elected governor in 2010.
His spokesman, Cullen Werwie, had no comment Friday on the investigation closing and referred calls to Walker's campaign. A spokeswoman there did not immediately return calls.
The investigation began in May 2010, six months before Walker was elected governor.
Walker hired high-profile criminal defense attorneys from Chicago, started a legal-defense fund that grew to $200,000 through the end of 2012 and met voluntarily with prosecutors in April. He always maintained his innocence and said he did not know that county workers were illegally campaigning while on the job. Walker said he had built a firewall to ensure county workers were not ordered to do campaign work while on county time.
Democrats insisted that evidence uncovered during the investigation showed that Walker was involved in illegal campaigning.