Huckabee plays well to the low-info evangelical voter. Maybe not so well anymore after already having been through the mill once, but that's his voting block.
If Cruz can put together a reasonably strong coalition of the Ron Paul libertarians, the Huckster's evangelicals, and also carry the TEA Party banner, he could do quite well in Iowa and South Carolina.
He'd be crushed in New Hampshire (maybe, depends on how libertarian they're feeling and if Rand is out after Iowa), but with strong showings in the other two, he can afford it.
Ideally, Cruz and Walker go 1-2 (either order) in Iowa, Walker wins NH, and Cruz wins SC. That pretty much makes it a two-man race early, and prevents the sort of conservative in-fighting that gave us McCain and Romney.