CNNMark Cuban thinks stocks could collapse into a bear market ifDonald Trumpbecomes US president.

The investor and reality-TV star told CNN on Monday that stocks could fall 20% if the presumptive Republican nominee wins in November.

He said investors would not be able to put up with the uncertainty attached to a Trump presidency.

“When youre flip-flopping, when youre not sure what the candidates going to say from one thing to another, that uncertainty potentially asthe president of the United States thats the last thing Wall Street wants to hear,” Cuban told CNN's Erin Burnett.

“I can say with100% certainty that there is a really good chance we could see a huge, huge correction” that could be as much as 20%, he said.

Cuban told CNN that it seems Trump hasn't done extensive homework on some the economic issues facing America, including the ones he says he'll fix.

But he gave Trump credit for shaking up the Republican establishment. Hetold CNNMoney last week that he had been asked to runagainst Trump, but thought it was too late.

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