Three GOP Senators Fight Against Koch Brothers Critics on Election Spending

Sen. Ted Cruz: 'I admire Charles and David Koch.'

"There are a bunch of Democrats who have taken as their talking point that the Koch brothers are the nexus of all evil in the world," Cruz continued. "I think that is grotesque and offensive."

Rubio asserted that some on the left criticize the Kochs for their political spending, but welcome campaign cash from friendlier sources.

“The people who seem to have a problem with it are the ones that only want unions to be able to do it, their friends in Hollywood to be able to do it and their friends in the press to be able to do it,” Rubio said.

Rubio used the example of billionaire Tom Steyer, who donated heavily to Democratic candidates in 2014, arguing that while he doesn't agree with Steyer's views, he stands by his right to spend money to promote them.

"There is a gentleman out there who has radical environmental ideas who has spent tens of millions of dollars, lost most of his races," Rubio said. "But spent tens of millions of dollars attacking Republicans that don't want to impose his radical environmental agenda. He has a right to do that."

Paul acknowledged that special interests can have a negative influence on government, but said the only special interests he's concerned about "are those who do business with government, get government contracts, take the government money and then try to get more contracts."