Story highlights "I think he's nuts. He's the grandson of German immigrants. He ought to be ashamed of himself," he said

"It's very divisive. It's not the kind of America I believe in and I don't think it's the kind of the America that most Americans believe in," Dukakis said

Washington (CNN) Former Democratic presidential candidate Michael Dukakis called Donald Trump "nuts" Friday over his views on immigration, adding that he believes Bernie Sanders should stay in the Democratic primary fight.

"I think he's nuts," the 1988 Democratic nominee told CNN's Wolf Blitzer. "He's the grandson of German immigrants. He ought to be ashamed of himself."

"I'm very proud of my background," said Dukakis, whose parents immigrated from Greece. "This is the guy who's the grandson of somebody who came over from Germany. And I don't know what he's talking about for one thing. It's preposterous."

The former Massachusetts governor -- whose failed presidential bid will be prominently featured in CNN's new episode of "Race for the White House" that airs Sunday at 9 p.m. ET -- also called Trump's plan to build a wall "ridiculous."

"It's very divisive. It's not the kind of America I believe in and I don't think it's the kind of the America that most Americans believe in," Dukakis said. "I hope at one point, he's going to start addressing real issues facing this country."

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