The billionaire industrialists Charles and David Koch are known for the many millions of dollars they've poured into conservative causes.
Among the beneficiaries: Wisconsin Gov. Scott Walker, the grassroots group Americans for Prosperity and the anti-regulation Mercatus Center.
And then there's the Cato Institute, a think tank that's a cornerstone of the libertarian movement. Now the Koch brothers are trying to take control of Cato away from its president. And many libertarians are furious.
The fight became public this month, when the Kochs sued Cato.
But NPR's Peter Overby explains on Morning Edition Tuesday how the showdown has been brewing for 20 years.