The outcome of the Iowa caucuses can change presidential races.
Since 1972, the Iowa caucuses have been the first time Americans vote for a potential president.
The winner gets a spurt of momentum and media attention.
However, the majority of winners have gone on to lose the Presidency.
In 2016, Ted Cruz won in Iowa only to lose the nomination to Donald Trump.
In 2012, Rick Santorum won the Iowa caucus.
Mitt Romney later won the nomination.
In 2008, Mike Huckabee won the Iowa caucus.