I honestly don't know if it's true, but Chris Stirewalt is *always* in the Fox News "Brain Room" on big election nights. He has also stated "I'm very proud of our Fox News polls" several times in a tone that suggests he might work on the polls.
I admit this is NOT "evidence" that Stirewalt is behind the FNC polls, but - from what I've recently seen - he always seems very defensive of them whenever anyone criticizes / questions the FNC polls.
Dana has pointed out repeatedly that Stirewalt IS Fox polling. They introduce the fat pig that way.