The super-PAC backing Scott Walker has many wealthy backers, but its single biggest contributor is Diane Hendricks, who ponied up $5 million. A billionaire through the roofing supply business she and her late husband founded, Hendricks has been one of Walker's top benefactors since he first ran for governor. In 2012, Hendricks was the biggest donor to Walker's campaign to stave off a union-led recall effort, and now she's stepped up for him again.