Ben Carson in a Presidential Debate..

[RFayette 🇻🇦]

He would get torn apart because he's an idiot, not because he's "soft spoken".

Come on, neurosurgeons are pretty much by definition "not idiots," though some of Carson's statements definitely call his knowledge about various public policy topics into question. 

If Carson is the nominee, he'd almost certainly lose, but perhaps not by as much as some might think (I could see him coming within 5 points or so).  A lot of people would likely appreciate his subdued tone in a debate.