After a tough week of media scrutiny, Herman Cain retreated to friendly turf Friday with an address to a conference sponsored by Americans for Prosperity, a grassroots conservative group Cain worked for prior to launching his presidential campaign.

Liberals have criticized Cain for his connection to the group, funded in part by Charles and David Koch, energy moguls who own one of the largest privately owned companies in the country. The Kochs bankroll many conservative and libertarian causes. But on Friday, Cain was anything but apologetic.

"I'm very proud to know the Koch brothers," Cain told the crowd. "Just so I can clarify this for the media. This may be a breaking news announcement. I am the Koch Brothers' brother from another mother. Yes. I'm their brother from another mother! And proud of it!"

AFP enlisted Cain in 2005 to head its Prosperity Expansion Project, and he traveled the country for the group. Mark Block, Cain's campaign manager, formerly led AFP's Wisconsin state chapter and Rich Lowrie, Cain's economic adviser who wrote his "9-9-9 Plan," sat on AFP's board of advisers for three years.

Over the past couple of years, Koch Industries has become Enemy Number One on the left for its financial support to Republican political organizations. At the AFP conference, activists from the local Occupy Wall Street protest in Washington, D.C. are planning to target the company in pickets outside the convention center.

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