Amy Walter:

No, it's pretty remarkable that, of all the candidates, this is the one candidate who has gone literally from zero to the lead. Back in March, I think he was polling somewhere around 1 percent or 2 percent.

But what's remarkable about Iowa right now, we have had four polls since March from The Des Moines Register, which is the gold standard of polling in the state. And while it's very volatile, right, we have had three different leads in these polls, so four polls, three different leaders, they have been the same four people.

It's been of the pool of four people. We have a huge field, but the same four people are mentioned as either one, two, three, or four since March.

And so what we're seeing is, yes, there is some volatility here, but it's not, at this point, opening a lane for somebody who is not in those top four.