It seems like every time a new Iowa poll comes out, the media begins buzzing about whoever is leading. But, history tells us that Iowa is neither a good prognosticator of who gets the nomination for either party, nor a good predictor of the ultimate President. Cases, in point are as follows, with 40 years of data from Wikipedia.
Picking the Party's Nominee
For Democrats since 1976, Iowans -- putting 2nd term presidential runs aside -- have only picked the party's nominee 4 times; Barack Obama (2008), John Kerry (2004), Al Gore (2000), and Walter Mondale (1984). On the Republican side, Iowans only picked their party's ultimate nominee 3 times: George W. Bush (2000), Bob Dole (1996), and Gerald Ford (1976).
Picking a First-Term President
For the Democrats, only one person has been picked to become the party's nominee, and then gone on to be President. That was Barack Obama in 2008. Similarly, for the Republicans, only George W. Bush accomplished the same feat in 2000. This fact should scare Hillary Clinton to death, if she, as it almost seems inevitable, wins Iowa. It should also scare whoever wins on the Republican side. Clearly, the odds are against the Iowa victor becoming President.
I would be remiss if I did not mention that the only two sitting Presidents who won Iowa and lost the General Election were Jimmy Carter for the Democrats in 1980 and George H.W. Bush for the Republicans in 1992.
Clearly, the political junkies will find Iowa an adrenaline rush, but in reality, it is no big deal. I mean, no offense to the people of Iowa, but being first may simply mean that people aren't really paying attention yet.
The Iowa Caucuses: History: https://en.wikipedia.org/wiki/Iowa_caucuses