As the US presidential election looms, the billionaire Mark Cuban has emerged as an energetic campaign surrogate for Kamala Harris. Making the case for business leaders to support the Democrat over Donald Trump, Cuban has drawn on his experience (in tech, investments, healthcare and now sports, as minority owner of the Dallas Mavericks NBA team), celebrity (as a lead “shark” for 15 seasons of ABC’s Shark Tank) and willingness to confront Trump-supporting billionaires, Elon Musk prominent among them.

The road has not been smooth. Last week, Cuban clashed with congressional progressives after criticizing Lina Khan, chair of the Federal Trade Commission, over her tech-sector antitrust work. That issue and others, including Cuban’s thoughts on Trump’s championing of tariffs and the perennial question of whether Cuban harbors presidential ambitions of his own, are addressed below, in emailed answers to 10 questions posed by Guardian writers and editors.

Why did you start speaking up in support of Kamala Harris? Do you coordinate with the campaign, or set your own course?

I think she would be a far better president than her opponent. And I do my own scheduling. We are discussing them setting some things up for closer to the election [on Thursday, Cuban appeared with Harris at a rally in Wisconsin].

Can Harris appeal to white working-class voters? If so, how?

I think her appeal to everyone is the same. She is ethical, not an ideologue, open-minded, analytical, she wants to solve problems no matter where they come from. She has said she would appoint a Republican to her cabinet.

She understands technology and the importance it has to national security, far, far better than her opponent. When Donald Trump talks about AI [artificial intelligence] he only talks in term of how much electricity it uses. Kamala understands the strategic, economic and defense opportunities it presents.

I have worked with her team to bring pharmaceutical costs down significantly and that’s just the beginning in her reducing healthcare costs.

Why are men such a problem for the Harris campaign? How would you appeal to them?

I think we are living in a world of memes. Donald Trump does a great job talking in soundbites rather than with substance. Soundbites are more meme-friendly. I also believe that the algorithms of social media reinforce those memes, which benefits Trump with men.

You have known and dealt with Trump for some time. Do you think he has deteriorated with age, as his critics charge? If so, how?

Yes. His speeches are longer, more rambling. The number of non-sequiturs continues to grow. He used to try to give direct answers to questions. I don’t think he even tries or is able [to do that] any longer.

What would a second Trump presidency mean for the US, and why should businesspeople choose Harris over Trump?

Stability is the key for larger businesses. They don’t want to wake up to a tweet or a new tariff that impacts their business, because Donald got mad at someone.

I think tariffs are also a big issue for businesses of all sizes: 10%, 20%, 60%, 200%, they are paid by the importer and passed on to customers.

Trump uses tariffs as a threat to American companies, even when it helps their foreign competitors. A 200% tariff against John Deere makes their foreign competitors less expensive [Trump threatened the tariff if the company were to move some production to Mexico], even after a 10% or 20% tariff against their products. That’s insane.

So many small entrepreneurs import products. But tariffs could literally put small retailers and manufacturers out of business.

Small businesses don’t have the pricing elasticity of larger companies. They can’t pass on the incremental and administrative costs associated with tariffs.

Trump doesn’t understand how he will put small retailers and manufacturers out of business: 75% of manufacturers have fewer than 20 employees. Tariffs on the inputs to their manufactured products could put them out of business.

Under Kamala, small-business benefits would benefit significantly. Ninety-seven per cent-plus of small companies are Sub S or LLC, which means they are taxed at their personal rates. For all of those entrepreneurs, if their incomes are $400,000 or under (which is 95% or more), their taxes won’t go up and will probably go down.

Kamala is also proposing increasing the ability to expense startup costs up to $50,000 (a 10-time increase), and she has childcare tax credits and tax credits for newborns that will allow parents to get the help they need to keep their businesses running.

A lot of other successful business people – Elon Musk, Peter Thiel – are backing Trump. What’s his appeal? Why do you think they are wrong?

I can only guess. I think they believe they can manipulate him.

Has Harris told you how her business policies will differ from Biden’s, and can she reconcile her big-business-friendly stance with her stand against price-gouging?

She has understandably not wanted to throw her current boss under the bus. But the differences are stark. She came in at 28% for corporate and capital gains, far lower than what Biden wanted. She doesn’t want a tax on unrealized capital gains. I think she has shown she will be far stricter on the border.

Why do you think a President Harris – or presumably President Trump in a second term – should remove Lina Khan as chair of the FTC, over her stance on antitrust issues? Are you prepared for the “brawl” with progressives that Alexandria Ocasio-Cortez has promised on the issue?

I should rephrase what I said before [“If it were me, I wouldn’t” keep Khan, and: “The bigger picture is, she’s hurting more than she’s helping,” to Semafor last Tuesday]. I gave my opinion, which was that while I think Lina has done a great job with PBMs [pharmacy benefit managers], scam companies and more, I prioritize AI, because of its importance to our economy, and believe our largest AI companies should not be broken up. That said, I have no intention of requesting or suggesting that she be fired.

You have said you would have supported a business-minded Republican such as Mitt Romney or Jeff Flake had they stood for president. Can that sort of Republican ever be nominated again? What do you say to such Republicans – Romney, Larry Hogan and others – who won’t back Trump but will not vote for Harris?

I think they will vote for her. They just don’t want to say it and deal with the blowback. And my comments on Jeff and Mitt were if Biden was the candidate. I would vote for Kamala over either.

I can’t stress enough the importance of Kamala coming to the center. I think she will do the best job representing all Americans, not just Democrats or Republicans. I think of her uplifting approach to her campaign: not only has she tried to remain positive, she has not criticized anyone beyond Trump and JD Vance.

That’s important. Not a negative word about their supporters. Just an attitude that tries to bring people together. Compare that to the hateful rhetoric of Trump. I mean, saying he hates Taylor Swift, just because she didn’t support him, is emblematic of who he is and how different he and Kamala are.

Were you ever tempted to run yourself – as a Romney-esque business-minded Republican or on any other platform? Could you be yet?

For about eight hours. Then I woke up. :)