Claiming there’ll be a stock crash if someone is elected is not stock manipulation.
If he made materially false statements, about a stock itself, deliberately meant to cause the economy to crash, then it would be a different story, but nothing he said was materially false, as he was just saying an elected candidate would be bad for the economy, in his opinion.
It would be stock manipulation if he acted upon insider information to manipulate the stock price, or used proven, materially false statements about the reality of a company/stock to deliberately drive the stock down in price.