Dan Pfeiffer, former senior advisor to President Barack Obama, said on CNN Thursday that the Republican presidential candidate he thinks Democrats should fear the most is Florida Senator Marco Rubio.
"Who will the Democratic Party do worse against last night? Who was the strongest candidate last night?" host Jake Tapper asked.
"Marco Rubio by far," Pfeiffer replied without hesitation. "I think the best arguments Republicans will have against Hillary Clinton, the most likely nominee, is a future versus past. And he embodies the future."
"He is the only candidate who has had an optimistic future-looking — an optimistic way of talking about the conservative message," he added.
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