Define "big way?" Obviously if Cruz wins SC, several of the Super Tuesday states, it's a different game. So far, there is no evidence he can, or will. The evidence he can, or will, even win IA is completely mixed---2 polls have him up (including the "shock" 10 point poll) and three polls have Trump up. These things usually (and there's always an exception) tend to move like waves, ebb and flow. The leading candidate gains, loses some, gains back more.
Just my hunch, but I think Cruz has hit his high point in IA at about 25-27, and will stabilize and even come down a tad. I don't think he'll ever fall below 20, which is his natural constituency + Carsonites.
I would define “big way” as in 5-10+ plus in national polls.
I disagree in Iowa, I think he continues to move up (possibly even to 50%?).
We’ll see.