David Gergen: “If Rick Santorum wins, he has a very strong argument that this ought to be a one-on-one with Romney.”

I think the turning point that came were the midterm elections. The fever broke with those midterm elections. And what we've seen since then is a steady decline in Trump's credibility and in his position with the American people, and a…

I think a lot of Americans do see it as disqualifying. And they're worried about it.

Sadly, you know, I think for a variety of reasons he should not. I just, I don't think either Trump or Biden should be running.

It's very, very big. Not legally, but politically, it's a very, very big deal.