Koch, who helped found the conservative non-profit Americans for Prosperity, said he plans to remain active in politics after the election, USA Today reported Friday.
"We're in this for the long haul," he told reporters Thursday in Tampa at the Republican National Convention.
The New York businessman and his brother, Charles, have been cast as villains of the right by Democrats, USA Today said. Koch dismissed the characterization, saying he also donates to arts groups and cancer research.
"I try to do things in life that make the world a better place," Koch was quoted as saying. "I'm a Republican, and I support fiscal responsibility, and I ... like to speak out."