Guys, RELAX!
Iowa only serves to trim off the bottom candidates. Since it is a proportional system, it means that the top three candidates will get about 10 delegates +/- 2 delegates.
It is not so much a win as a tie with the top three.
Cruz, Trump and Rubio all know that it is a marathon and not a sprint. Each of those campaigns will now refocus on the next state and then the next state etc. That is the way that things will be until we start getting to the winner take all states.
Remember, these early caucuses are designed to eliminate the bottom candidates. I encourage all candidates who received less than 2 delegates from Iowa to drop their campaign and endorse one of the other candidates. Likewise, to those that have supported a candidate that got less than 2 delegates, please consider one of the other candidates for your support.
The sooner that the GOP field is narrowed, the better off the party will be going into the general election.
There are actually only about 12 true "winner take all" states. The rest are either proportional (some with a threshold to receive any delegates), or they are a hybrid where the winner of each congressional district wins the delegates for that district, and the overall state winner wins a few extra delegates. California follows that model, for example. So if Trump, Cruz and Rubio continue to battle it out past March, it is likely that none of them will be able to get a majority of delegates before the convention.