David and Charles Koch, the wealthy brothers whose donor network has given hundreds of millions to Republican causes and candidates in the past, aren't going to pour cash into the third-party bid of Libertarian Party candidate Gary Johnson – and reportedly won't spend a dime on GOP candidates in 2016.

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A spokesman for the Kochs on Thursday contradicted a report by The Daily Caller – citing a source within the Johnson campaign – that they planned to spend "tens of millions of dollars" to support Johnson, who is all but assured to win the Libertarian presidential nomination.

Johnson, a former two-term Republican governor of New Mexico, also ran for president as a Libertarian in 2012, but barely garnered one percent of the vote.

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8 PHOTOS David Koch See Gallery Cashed out: Koch brothers sit on wallets in '16 David Koch Built a Toxic Empire — with Human Consequences Miliarder David Koch Meninggal Dunia Businessman David Koch arrives at the Metropolitan Museum of Art Costume Institute Gala Benefit celebrating the opening of "Charles James: Beyond Fashion" in Upper Manhattan, New York May 5, 2014. REUTERS/Carlo Allegri (UNITED STATES - Tags: ENTERTAINMENT FASHION BUSINESS HEADSHOT) Businessman David Koch arrives at the Metropolitan Museum of Art Costume Institute Gala Benefit celebrating the opening of "Charles James: Beyond Fashion" in Upper Manhattan, New York May 5, 2014. REUTERS/Carlo Allegri (UNITED STATES - Tags: ENTERTAINMENT FASHION BUSINESS HEADSHOT) Businessman David Koch arrives at the Metropolitan Museum of Art Costume Institute Gala Benefit celebrating the opening of "Charles James: Beyond Fashion" in Upper Manhattan, New York May 5, 2014. REUTERS/Carlo Allegri (UNITED STATES - Tags: ENTERTAINMENT FASHION BUSINESS) EXCLUSIVE. Julia and David Koch, and their son host a party taking place at their home for the Charles Evans PCF Pro-AM TOUR 2012 Hamptons Tournament, benefiting the Prostate Cancer Foundation, in Southhampton, NY on August 18, 2012. The reclusive David Koch has a net worth of $25 billion. He is thought to have bankrolled the tea party, a connection however which he is evasive about. Strongly anti-Obama, he and his brother Charles have poured an estimated $400,000 million into the 2012 campaign. Photo by Art Seitz / ABACAUSA.COM Businessman David Koch arrives at the Metropolitan Museum of Art Costume Institute Gala Benefit celebrating the opening of "Charles James: Beyond Fashion" in Upper Manhattan, New York May 5, 2014. REUTERS/Carlo Allegri (UNITED STATES - Tags: ENTERTAINMENT FASHION BUSINESS HEADSHOT) U.S. businessman and philanthropist David H. Koch is seen with an unidentifed guest as he arrives for the Metropolitan Museum of Art Costume Institute Gala 2015 celebrating the opening of "China: Through the Looking Glass," in Manhattan, New York May 4, 2015. REUTERS/Andrew Kelly Up Next See Gallery Discover More Like This HIDE CAPTION SHOW CAPTION of SEE ALL BACK TO SLIDE

The Kochs originally planned to spend nearly $900 million on the 2016 campaign but have since scaled back their budget for the entire cycle to just $40 million, as part of an overhaul of their free-spending approach to politics.

"Reports that we are supporting or considering supporting any third party presidential candidate are false," Philip Ellender, a spokesman for the Kochs, told CBS .

Johnson also said he was not expecting a sudden influx of cash.

"To my knowledge, it's not happening," he told the Washington Post . "That's not to say it isn't, but it would be a surprise to me. We tried to talk to the Kochs during the last cycle, and we couldn't do it. There are a lot of people who are expressing interest, in a big way, to be a part of this, but I'm not naming names. I can say that I haven't reached out to the Kochs."

Given the Kochs' longtime affinity for libertarian causes – and and their disappointment with the results of the Republican nominating contest – raised hopes among conservatives longing for an alternative to presumptive Republican nominee Donald Trump.

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But – for the time being – the Kochs seem burned out by how little their millions have done in shaping national policy. They failed to unseat President Barack Obama in 2012, despite spending more than $400 million in that election cycle.

And while Republicans in 2014 wrested control of the Senate and expanded the House GOP majority to historic proportions – due in no small part to the $300 million spent by the Koch network – the billionaire brothers have few policy victories to show for it.

Instead, they are "unlikely to spend a dime on the 2016 presidential election," according to a National Review report detailing their withdrawal from federal races this year.

"And as two of wealthiest men alive, they could instantaneously bankroll a campaign against Clinton on their own," the National Review explains.

"As of now, however, Koch insiders say that's unlikely to happen," it continues. "If they are right, Republicans will go into this fall's elections without the full support of their biggest benefactors, creating a void that could have lasting consequences for the GOP on the national stage."

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