A prominent economist trying to influence the incoming Trump administration's economic policies is facing criticism from conservative groups over his organization's liberal donors and past criticism of President-elect Trump's agenda.

Oren Cass, who previously worked on both of Mitt Romney's presidential campaigns, is the founder and chief economist of American Compass, a conservative think tank that has made inroads with multiple prominent Republican lawmakers in Congress.

Over the past year, Cass' philosophy has reportedly gained traction in some pro-Trump circles, but several conservatives have taken issue with his increased influence and worry his policies will undermine the Trump agenda based on his past anti-Trump comments. During a May 2021 interview, Cass likened Trump to "an earthquake" because he believed Trump was a "disaster in many ways."

"Self-proclaimed ‘conservative’ Oren Cass and his American Compass is not, and will never be, viewed as a legitimate voice in Republican policy circles. CNBC’s Joe Kernen got it right when he called them 'bonkers, walking quacking uniparty progressivism.' And their funding only proves that," Club for Growth President David McIntosh told Fox News Digital.

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"As American Compass continues to stay in business thanks to generous donations from radical left-wing organizations like the Hewlett Foundation and the Omidyar Network, Club for Growth is proud to stand with President Trump and the overwhelming majority of Republican voters who support actual conservative policies, like the proposals described in our Foundation’s recent "Freedom Forward Policy Handbook," including: tax cuts, spending cuts to reduce the deficit, deregulation to boost American manufacturing, American-first energy policies, school choice and worker freedom," he continued.

A significant chunk of American Compass' funding comes from a handful of foundations tied to liberal causes, including almost $2 million from the William and Flora Hewlett Foundation and the Omidyar Network, which has provided 11% of American Compass' funding and is led by a founder described as "notable for funding liberal-in-conservative clothing groups that target former president Donald Trump and his supporters."

American Compass is also associated with the "Reimagining Capitalism Partners" fund, which includes the Center for American Progress, Sixteen Thirty Fund-linked Groundwork Action, Progressive Caucus Action Fund, Tides Advocacy and Demos, a socialist think tank.

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Cass’ group has also received over $200,000 from the Rockefeller Foundation, a multibillion-dollar foundation that has bankrolled several left-wing causes, including radical environmental groups and "Imagining America," a "coalition of colleges engaged in left-wing curriculum development," according to the Capital Research Center. 

The San Francisco Foundation, which has funneled hundreds of millions of dollars to far-left groups, gave $100,000 to American Compass.

When Fox News Digital pressed Cass on his organization's funding and criticism from rival conservative groups, he blasted the "anti-tax zealots" criticizing his organization.

"American Compass advocates for limited government and a commitment to paying for the government that we have rather than leaving the bill to our children," Cass told Fox News Digital. "Anti-tax zealots can lobby for larger deficits if they want, but conservatives are under no obligation to follow them into the fiscal ditch." 

In addition to the money that American Compass has received from left-wing groups, its advisory board includes multiple Democrats, including Ganesh Sitaraman, who served as a senior fellow at the Center for American Progress and has been a longtime adviser to Sen. Elizabeth Warren, D-Mass., dating back to her 2012 Senate campaign. 

Matt Stoller, the research director at the American Economic Liberties Project, which received at least $500,000 from George Soros’ Foundation to Promote Open Society and at least $230,000 from the Omidyar Network Fund, is also on the advisory board and has donated tens of thousands of dollars to Democrats.

Tom Hebert, the director of competition and regulatory policy at Americans for Tax Reform, blasted Cass as an "anti-Trump activist" in a statement to Fox News Digital.

"The American people returned Donald Trump to the White House with a strong economic mandate: cut taxes, slash job-killing regulations and promote worker freedom. Oren Cass founded American Compass as a ‘post-Trump’ organization and opposes the Trump economic agenda at every level, even calling the landmark Trump tax cuts an ‘expensive failure,’" Hebert said. 

"Cass is not a conservative. He’s an anti-Trump activist that MSNBC has on speed dial to undermine Trump’s second-term agenda."

In addition to Hebert’s quote, Americans for Tax Reform published a piece in July with the headline, "Who Said It, Oren or Warren?" The piece pointed to the tax plans of Sen. Warren and Cass’ American Compass, which were both published a month earlier and include multiple quotes from Warren and Cass, asking readers to identify the source of each quote.

"Warren’s plan calls on Democrats to reject extending the Trump tax cuts," the piece says. "The proposed budget released by Oren Cass’ American Compass, which describes itself as ‘the flagship for a healthier and more responsive post-Trump conservative movement,’ calls for the full expiration of the 2017 Trump tax cuts, would increase the corporate rate to the Biden-preferred level of 28%, and backs Warren’s call for a financial transaction tax."

Americans for Tax Reform went on to call American Compass "left-wing" and said Cass was the "leader of the tax-hiking American Compass" in a separate post from earlier this year due to his opposition to Trump’s tax cuts.

Cass was mocked earlier this year after he went on CNBC and suggested that lowering taxes and the corporate tax rate is not "conservative," adding, "There is nothing conservative about that … absolute radical nonsensical notion." 

The clip prompted Richard Stern, who serves as the director of the Heritage Foundation's Grover M. Hermann Center for the Federal Budget, to sound off on Cass, saying, "[Cass on] CNBC this morning defending the uniparty's attempt to steal your money and put it in their hands — and to stop capital from flowing to new and small businesses. With ‘friends’ like this, who needs socialists."

During a C-SPAN interview over the weekend, Cass praised some aspects of Trump's first administration, saying the United States "made a tremendous amount of progress" by implementing a "much more aggressive trade policy and confronting China." He also praised the incoming Trump-Vance administration on some of its Cabinet picks, including calling Sen. Marco Rubio, R-Fla., an "excellent" State Department pick because of his work sounding the alarm about China being our "main adversary." 

He added he hopes the administration will have a "labor policy that is much more focused on the interests of workers," pointing to Vice President-elect JD Vance's past comments and saying commerce and labor are the "heart of our economic policy."

Despite Cass offering some praise of Trump, he has been a longtime critic of Trump's 2017 tax cuts, calling them an "expensive failure" and saying Trumpism is facing an "inevitable expiration" and adding in September 2020 that Trump is "building no intellectual foundation, no institutional infrastructure and no policy agenda."

After Trump's 2024 election victory, Cass continued to signal opposition to Trump's tax policy. 

"Well, I think we have today a politics where both candidates go around talking about how they`re just going to cut everybody`s taxes," Cass told PBS Nov. 10. "And, of course, everybody likes a tax cut. But I don`t think those are the things that are going to turn our economy in a much better direction."

During another interview from earlier this year, Cass said one of the things he thought was "most encouraging" was that there aren't "mini Trumps" and that he is "extremely encouraged" by the post-Trump era Republican leaders he is seeing.