“He has moved with the neoconservatives,” Buchanan said. “At his speech over at the Brooking Institution, he not only, you know, said that Putin was basically a weak leader, he said we should get involved in Syria — and maybe, militarily, we’ll have to attack Iran. He’s with Joe Lieberman and [John] McCain and Lindsay Graham and that crowd. And I don’t think that’s a winner right now.”

Buchanan also said Rubio’s youthful appearance, compared with Romney, is a potential problem.