Mavericks owner Mark Cuban was the target of one of a series of tweets unleashed by President Donald Trump on Sunday morning.

At 8:23 a.m. ET, Trump wondered why Cuban’s allegiance to him changed over the course of the presidential election.

I know Mark Cuban well. He backed me big-time but I wasn't interested in taking all of his calls.He's not smart enough to run for president! — Donald J. Trump (@realDonaldTrump) February 12, 2017

Cuban’s response:

Trump’s tweet comes after Cuban’s comments to the Star-Telegram that while CEOs should be careful about how they talk politics, they should “do what (they) think is right. Be an American citizen first.”

Cuban added, “In the bigger scheme of things, our country benefits from peaceful activism a lot more than it benefits from one more shoe being sold, or one more basketball ticket being sold, for that matter. The people that say stay away from politics are the people that are looking for politics.”

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While Cuban has not held back in his criticism of Trump, the Mavs owner did back Trump early in his candidacy. In September 2016, Cuban explained to Bloomberg why his support shifted to Hillary Clinton.

In a subsequent tweet Sunday morning, Cuban reminded Trump about why he changed his allegiance while sharing what appears to be a hand-written note he received from the eventual president.