This was surprising to see.
Billionaire businessman Mark Cuban is taking aim at a major tax proposal backed by California Democrats, warning that the plan could drive entrepreneurs, investors and valuable startup companies out of the state.
The outspoken entrepreneur delivered his warning during a public exchange with Democratic Rep. Ro Khanna of California over Proposition 40, a November ballot measure that would impose a one-time 5% wealth tax on California billionaires.
Cuban’s criticism is notable because he has frequently clashed politically with President Donald Trump. But when it comes to the economic consequences of higher taxes on wealthy entrepreneurs and investors, Cuban is now making an argument that closely resembles warnings Republicans have issued for years.
His message to Khanna was simple:
“Ideology is not a strategy.”
The disagreement is quickly becoming part of a much larger debate over California’s economy, taxes and whether aggressive efforts to target wealthy residents could ultimately cost the state businesses, jobs and investment.
Mark Cuban Challenges Democrat Ro Khanna
The controversy erupted after Khanna celebrated the California Democratic Party’s support for Proposition 40.
Khanna argued that California voters want Democratic leaders who are willing to stand up for working Americans rather than the billionaire class.
Cuban pushed back.
While acknowledging his friendly relationship with Khanna, Cuban argued that the congressman was overlooking an important economic reality involving California’s booming technology industry.
Silicon Valley continues to produce enormously valuable startup companies, particularly as investors pour billions of dollars into artificial intelligence and other emerging technologies.
When one of those companies suddenly receives a valuation of $10 billion or more, its founders can become billionaires on paper almost overnight.
But there’s a catch.
Those founders don’t necessarily have billions of dollars sitting in their bank accounts.
Cuban Warns About “Cash Poor, Stock Rich” Entrepreneurs
Cuban described many successful startup founders as “cash poor, stock rich.”
That distinction sits at the heart of his argument against California’s proposed billionaire tax.
An entrepreneur might own company shares valued at $1 billion while having only a small fraction of that amount available as cash. A tax calculated using the founder’s overall net worth could therefore create an enormous financial obligation without providing the individual with the cash needed to pay it.
Cuban questioned how founders could realistically produce hundreds of millions of dollars to satisfy such a tax.
The concern is particularly relevant to privately held technology companies because founders may face restrictions on selling their shares. Even when shares can be sold, unloading a significant portion of an ownership stake can potentially affect control of the company and other investors.
For Americans who have spent decades building businesses, retirement portfolios and investments, the controversy raises a broader economic question:
Should government tax wealth that exists primarily on paper before the owner actually receives that money?
Cuban Threatens To Move Investments Out Of California
Cuban didn’t stop at criticizing Proposition 40.
He warned that the measure could directly influence where he puts his own investment dollars.
Cuban said that if he were considering an investment in a multibillion-dollar California startup, he would ask the company to leave the state first.
He went even further, saying that not being located in California could become a prerequisite for receiving his investment money.
“If this passes, only idiot startup founders stay in Cali,” Cuban warned.
That statement could become ammunition for critics who have long argued that California’s taxes and regulations are making other states more attractive to businesses and wealthy residents.
The issue goes far beyond billionaires themselves.
When companies relocate, the consequences can potentially affect employees, suppliers, office space, local businesses and the tax revenue generated by economic activity surrounding those companies.
Supporters of Proposition 40 dispute the idea that the measure would cause serious economic damage and instead argue that wealthy Californians can afford to contribute more.
But Cuban clearly believes policymakers are underestimating how entrepreneurs and investors could respond.
California’s AI Boom Raises The Stakes
California remains home to Silicon Valley and one of the world’s most important technology economies.
The explosive growth of artificial intelligence has made that advantage even more valuable.
Investors have poured enormous amounts of money into promising AI companies, sometimes sending their valuations soaring before the businesses generate comparable levels of profits or cash.
That can make founders extraordinarily wealthy according to their estimated net worth while leaving much of that wealth locked inside company shares.
Cuban’s argument is that Proposition 40 could punish exactly the type of entrepreneurial success California should be trying to attract.
If founders believe becoming successful in California could expose them to a massive wealth-tax bill, they may have another reason to establish their companies elsewhere.
States such as Texas and Florida have spent years attempting to attract companies, entrepreneurs and wealthy residents from higher-tax states.
Cuban’s warning suggests California could unintentionally give those competitors another advantage.
Democrats Split Over Proposition 40
The billionaire tax has also exposed a significant divide inside the Democratic Party.
Progressive Democrats and organized labor groups have backed the proposal, arguing that extremely wealthy Californians should contribute more toward government programs.
Supporters say revenue generated by the tax could help finance health care and other public priorities.
But not every prominent Democrat agrees.
California Gov. Gavin Newsom has opposed Proposition 40, putting him at odds with supporters including Khanna and the California Democratic Party.
That creates an unusual political battle in which some of California’s most prominent Democrats are warning about the economic consequences of a tax being promoted by other members of their own party.
Cuban’s involvement adds another high-profile business voice to that debate.
Cuban’s Argument Echoes A Longtime Trump Warning
Cuban and President Trump have certainly not been political allies on many issues.
However, Cuban’s latest argument overlaps with a fundamental economic warning Trump and other Republicans have repeatedly made: Taxes and government policies can influence where businesses and investors choose to put their money.
Businesses do not necessarily have to remain in one state.
Neither do wealthy taxpayers.
In an economy where companies can relocate offices, employees and investments across state lines, policymakers must consider how taxpayers will respond to major changes in tax policy.
That is why the Proposition 40 debate could have implications far beyond California.
If the tax passes and California continues attracting entrepreneurs and investment, supporters could point to the result as evidence that fears of an exodus were exaggerated.
But if wealthy residents, startup founders and investors begin leaving or directing new investments elsewhere, opponents could argue that the measure produced exactly the consequences they predicted.
California Voters Face A Major Decision
California voters will ultimately decide the future of Proposition 40.
The ballot measure would impose a one-time 5% tax on billionaires, placing California at the center of America’s continuing debate over wealth, taxation and economic inequality.
Supporters see an opportunity to raise substantial revenue from residents who have accumulated enormous fortunes.
Opponents see something very different: a potentially dangerous experiment that could encourage some of the country’s most successful entrepreneurs and investors to take their money elsewhere.
Cuban clearly falls into the second camp.
His criticism carries additional weight because he understands the world of startups and venture investment firsthand.
The question voters must consider is whether California can collect billions of dollars from its wealthiest residents without changing their behavior—or whether the tax could ultimately push future investment, companies and jobs into competing states.
What Proposition 40 Could Mean For California’s Economy
The debate is ultimately about more than whether billionaires should pay higher taxes.
It is about what produces the greatest long-term benefit for ordinary taxpayers and workers.
Supporters believe the wealth tax could provide additional money for important government programs without increasing taxes on middle-class families.
Critics argue that protecting California’s tax base requires keeping successful businesses, entrepreneurs and investors inside the state.
Both sides are making dramatically different predictions about what would happen next.
Cuban’s position is clear: California should think carefully before assuming wealthy entrepreneurs will simply stay put and pay the bill.
And coming from a businessman who has often opposed Trump politically, that warning could attract attention from voters across the political spectrum.
With Proposition 40 headed before voters in November, Californians will soon decide which argument they find more convincing.