Iowa is the first state in the nation to begin the party nomination process in presidential elections. It has been that way since 1972. It is a unique form in the nation using caucuses rather than primary elections. As Iowa only awards 1% of the delegates it is rather inconsequential, except that it is first. This brings a great deal of attention to the state.
Beyond being first, what does Iowa tell us? Its track record in predicting the nominee for the Democrats is only 40%. With Republicans it is slightly better, but still only 50/50. So winning isn’t really predictive. As Iowa is not a winner takes all state and the delegates are distributed based on the percentage each candidate receives its practical meaning in the race for delegates is also subdued.