(CNN) Ben Carson gave a tepid explanation of his decision to endorse Donald Trump on Monday, saying even if Trump "turns out not to be such a great president ... we're only looking at four years."

Carson told Newsmax TV that he backed his former Republican presidential rival because "I'm a big picture guy."

"Even if Donald Trump turns out not to be such a great president, which I don't think is the case, I think he's going to surround himself with really good people," Carson said. "But even if he didn't, we're only looking at four years as opposed to multiple generations, and perhaps the loss of the American dream forever."

Noting that Trump would assemble a capable support system of "good people," Carson also revealed he was promised a role in a potential Trump administration.

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