Iowa is unique primary. Historically about 5% of voters participate in caucus. Low budget candidates can win Iowa with lot of leg work. Example: Santorum in 2012. Iowa has not been a good indicator of national primaries.
In my opinion, summary of first 4 primaries is a much better indicator. (IA, NH, SC, NV)
Then comes super Tuesday (12 states). Results here pretty much will determine the eventual winner.
RealClearPolitics added this poll moving down that New York Times junk poll that sat at the top all week long.