Charles Koch said he and his brother, David Koch, have voted for Democrats before, but said they would be be "more selective" with the candidates they back going forward.
But they didn't say who might have disappointed them over the years.
The Koch brothers were interviewed on MSNBC's "Morning Joe," where Charles said he didn't care which party a candidate comes from, so long as he or she worked to end the country's "two-tiered system." He said economic inquality is a major issue in this country today.
Charles Koch declined to comment on any specific candidate in the Republican primary, and said his brother David's praise of Gov. Scott Walker was wrongly interpreted as an intended donation of millions of dollars.