Mark Cuban
President Donald Trump tweeted that Dallas Mavericks owner, Mark Cuban is "not smart enough to run for president," Feb. 12, 2017. In this photo, Dallas Mavericks owner Mark Cuban apologized to Trayvon Martin's family for using the phrase "black kid in a hoodie" during an interview about racism, but reiterated that he meant what he said while speaking to Inc. Magazine in 2014. Reuters

President Donald Trump slammed the billionaire Dallas Mavericks owner Mark Cuban in a tweet on Sunday morning, calling him "not smart enough to run for president." Cuban and Trump have had issues ever since Trump's campaign heated up, and the former even made a campaign appearance for Hillary Clinton.

Cuban initially reacted to Trump's tweet with a "Lol," and then posted comments that he had made previously in an email in May 2016, criticizing Trump's campaign, and offering tips on how to improve. In one of his tweets, he also mocked Trump.

Cuban also mentioned that last April, when he had advised the then-candidate Trump, he had said: "To make it work you have to really dig in on the issues. It’s like the tech stuff today. The number of tech IPOs has fallen off a cliff. There are hardly any new public tech companies. So when you say there’s a bubble, it sounds like you are winging it. Which also makes it sound like your comments are based on who you talked to last. Which tells me you are getting bad advice. I get that a big part of your base doesn’t care about issue details, but to be president you have to dig in and know your [expletive]. You don't have to bore people with details but you have to learn the details."

Last week, Cuban, a businessman and a prominent television personality, encouraged CEOs of several companies in an interview with the Fort Worth Star-Telegram to "do what you think is right" and to "be an American citizen first."

"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," he said.

What prompted Trump's Twitter comments wasn't immediately clear, but in an email Cuban had sent to the Washington Post Sunday morning, he said he had been informed that the president was probably reacting to a New York Post story that mentioned him as a possible candidate in the 2020 elections. The NY post story said that Steve Bannon, Trump's chief strategist, had asked consultants to look into the backgrounds of four outspoken Democrats which included Ohio Sen. Sherrod Brown, Connecticut Sen. Chris Murphy, Colorado Gov. John Hickenlooper and owner Mark Cuban.

Reports also speculated over the fact that perhaps the president has a problem with Cuban's take on the tough spot that CEOs of many companies are currently in with Trump in the White House.