Not all candidates are as high profile as Trump. Getting to know the people who are running is what campaigning is all about. Walker was in the adjacent state. Cruz is just getting introduced.
The biggest thing Trump had going for him was the belief that he was the only one who could defeat Hillary. The polls have shifted on that as people have been introduced to other candidates and Hillary’s negatives have Ben mounting. This is not good news for Trump as people will begin to consider his warts and look to other viable candidates.
Iowa has not been good indicator of who wins nomination.
Huckabee & Santorum both won Iowa.
That makes sense, since barely 5% of Iowans bother to spend better part of a day to attend a caucus.
Even NH is not a a good indicator.
SC has been a much better indicator for the eventual winner.