(CNN) Sen. Sherrod Brown on Friday dismissed a possible independent presidential campaign from Howard Schultz, calling the billionaire former Starbucks CEO a "total idiot."

While talking with voters in Iowa's Dallas County after a farmers' roundtable, the Ohio Democrat, who's also considering a presidential bid, introduced himself to a voter who expressed concern about dark money in politics.

"Yeah, I mean you got this idiot Schultz running, maybe," Brown replied. "He's an idiot. I mean, he's a total idiot."

Schultz, who stepped down as chairman and CEO of Starbucks last year, told CBS's Scott Pelley he was seriously mulling a run for president as a "centrist independent" in an interview with "60 Minutes" that aired last Sunday.

He's called Sen. Kamala Harris' support for a "Medicare-for-all" proposal "not American" and "unaffordable," and Sen. Elizabeth Warren's proposal of a 2% annual tax on Americans with incomes over $10 million "an idea that has no merit."

Schultz isn't the only independent-minded billionaire considering a run for president. Michael Bloomberg, who was elected mayor of New York as a Republican and later as an independent, is also mulling a run, and has sided with Schultz on the prospect of Medicare-for-all.

However, in a statement released Monday, Bloomberg warned, "In 2020, the great likelihood is that an independent would just split the anti-Trump vote and end up re-electing the President. That's a risk I refused to run in 2016 and we can't afford to run it now."

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Schultz dismissed Bloomberg's concerns, saying, "I respect his decision. If he's going to run, he's going to run as Democrat. Good luck to him. I respect Mike Bloomberg. I have a different view."

Brown, who's in Iowa on the first leg of his "Dignity of Work" tour, with later stops in New Hampshire, South Carolina and Nevada, has spent most of his energy criticizing Trump, charging that the President "uses phony populism to distract from the fact that he has used the White house to enrich billionaires like himself."

When pressed about the threat of PAC contributions and dark money in politics by an Iowa voter, Brown was less specific about his own presidential ambitions. Asked specifically if he'd accept PAC money if he decides to make a presidential run, Brown would say only, "Probably not, but I haven't decided yet. I mean it's, I have records, my whole career standing up to interest groups, so it really doesn't matter what money, as long as it's, you know, but I have to decide that."