Former Starbucks chief executive Howard Schultz, who is thought to be considering an independent bid for the US presidency, has told students Donald Trump must not be re-elected.
Mr Schultz said at Purdue University in the state of Indiana that Mr Trump “must not serve a second term” in the White House.
Mr Schultz said on Thursday that Mr Trump’s presidency is “one of the most significant security threats America faces in the post-World War II era”.
He blamed Mr Trump for walking away from strategic alliances and starting a trade war that has cut market access for US farmers and industry.
He said Mr Trump “has poisoned our culture and our values”.
Prominent Democrats have urged the Seattle billionaire not to run as an independent.
They say it could split opposition to Mr Trump and make his re-election more likely.
Mr Schultz also called for tax and immigration reform and an end to partisan gerrymandering.