Story highlights Warren Buffett, the world's third-richest man, donated $25,000 to a pro-Hillary Clinton political group

The pro-Clinton Buffett has never before given to a super PAC

For Hillary Clinton 2016, Warren Buffett is putting his money where is mouth is and making his first-ever donation to an independent political group.

Buffett, the world's third-richest man and head of Berkshire Hathaway, gave $25,000 to Ready for Hillary, according to a source with the group. The donation, which will appear on the group's next disclosure form, is the max one donor can give under Ready for Hillary's self-imposed cap.

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Buffett has long disagreed with super PACs and in 2012 he stayed away from donating to them.

Buffett has been bullish on Clinton for years.

"Hillary is going to win, yeah," Buffett, an outspoken Clinton supporter, said at Fortune's Most Powerful Women Summit in October. "I will bet money on it. And I don't do that easily."

He also told CNN in 2012 that Clinton was the most qualified candidate for 2016.