I don't think Walker will quite click with Iowans when it comes to the retail stuff. We have two former Iowa winners in the field, and no one was picking them the previous summer. I think someone emerges out of the Huckabee/Santorum/Cruz/Carson four horsemen group, although nothing will come of that triumph in the long run.
This is the most sensible case, but the reason I have Huckabee coming close but not winning is because they all just have huge egos. Santorum barely won because Cain dropped and Bachmann and Perry's collapses were epic.
I don't doubt Cruz will fall apart from his high single digits, but I highly doubt by the scale of Bachmann - he is actually educated and ideologically consistent. Carson is smarter than Cain and polls fine. Santorum has no reason to drop unless he really doesn't get into a single debate over Perry. If he's polling 5-6% in Iowa by that time, he can point to the last surprise. I doubt he drops to endorse Huckabee.
There is no one with a legitimate case to drop out and the field is just too divided which is why its Paul for me right now. But there are too many contenders to judge this far just like 2012 when they gave it to Bachmann.
Santorum also needed Newt to collapse in December.
Walker could easily collapse though I don't think gaffes are the likely culprit; Iowa is the state of Jodi Ernst, Steve King and in presidential politics, Mike Huckabee. I'd say Walker has about a 50/50 chance to win it.
If so, I do think Cruz, Carson, Rubio and Huckabee are the likeliest beneficiaries but I wouldn't rule out Kasich, who is a serious Evangelical Christian. He won't necessarily resonate in Iowa, which he mocked as a crap state. And his Christian perspective may not be conservative enough for the Iowa GOP but it's possible he could cobble together a nice chunk between secular and Evangelical moderates. Looking forward to continued fighting between Walker, whose record is more conservative, and Kasich, whose record is less conservative/more effective.