A prominent Republican has criticized presidential candidate and billionaire Donald Trump as unworthy of the office of president of the United States. Former U.S. presidential nominee Mitt Romney gave a highly critical speech Thursday about front-runner Trump. In his speech, he urged Republicans to vote for other Republican candidates, and not Trump. “Here’s what I know. Donald Trump is a phony, a fraud,” Romney said. A Trump presidency “would be bad for American workers ... and families,” he said. Trump’s success has worried Republican Party leaders. The party is worried about many of Trump’s positions. That includes trade and immigration. Trump has called for building a wall between the U.S. and Mexico, deporting 11 million illegal immigrants, and barring Muslims from entering the country. “If Donald Trump’s plans were ever implemented, the country would sink into depression,” Romney said Thursday. He also said that the only “serious policy proposals that deal with the broad range of national challenges” in America come from other remaining candidates: Ted Cruz, Marco Rubio and John Kasich.