Fox has a bad habit in the prime time of skipping polls that favor Trump, which is about most of them except for Hannity who does report them. They mostly follow Murdock and the GOPE wishes. It looks like Trump still has Carson beat in Iowa. See the latest two IA polls under this one in Breaking News.
And yeah, I know Trump is kicking Carson all over the place. I’ve written about 10 plus states that Trump is beating Carson all over this thread several times. I’m all over it. ;-)
If Trump were to drop out Carson still would not win the first state outside Iowa. Trump’s support would go to Cruz.