Their political action committee contributed $43,000 to Walker's election campaign and gave more than $1 million to the Republican Governor's Association, which in turn paid for $3.4 million in attack ads against Walker's opponent, Milwaukee Mayor Tom Barrett.

A prank call to Walker by a blogger claiming to be David Koch provided more ammunition to the claims that the Koch brothers, and one of the groups they generously fund, Americans for Prosperity, are major players in Walker's plan to end collective bargaining for state workers. On Wednesday, Americans for Prosperity began running pro-Walker ads across the state that defend the governor's plan to end collective bargaining for public workers.

In an interview posted Thursday night on National Review Online, Koch executives told political reporter Robert Costa that the Koch brothers will ‘not stop' supporting free-enterprise initiatives, even in the face of intimidation from "the Left." They also said that David Koch and Walker have never met or spoken.