David Koch, a billionaire American libertarian and influential donor to conservative causes, has died at age 79 after a long battle with cancer, his brother Charles said Friday.
Koch retired last year as executive vice president of Koch Industries, the conglomerate he co-owned with his older brother and built into the second largest family-owned company in the United States.
"We wish for all to celebrate the life and impact of this most generous and kind man," Charles Koch said in a statement. "He believed he had a responsibility to a world that had given him so many opportunities to succeed."
Both brothers were a force behind the scenes in Republican politics, donating heavily to candidates and causes that reflected their conservative economic positions. But David was socially liberal - a supporter of abortion rights and same-sex marriage as well as a non-interventionist foreign policy.
Both brothers were recognized in 2015 for bipartisan work on prison reform in the United States.
Among those offering condolences was Secretary of State Mike Pompeo who, like the Koch brothers, is from Kansas.
David Koch ran as the Libertarian Party's vice presidential candidate in 1980, but later broke with it and swung to the Republicans.
He joined his brother Charles in financing a network of conservative organizations, in particular Americans for Prosperity, centered on demands for low taxes and deregulation with the aim of influencing US elections.
Those organizations helped fuel the rise of the Tea Party movement in 2010, mounting a frontal Republican challenge to former Democratic president Barack Obama.
The Kochs' power was such that in the next presidential elections, Republican candidates vied for their endorsement, attending exclusive conferences the brothers organized.