What do Bill Clinton, George H.W. Bush and Ronald Reagan have in common?
These former presidents all lost in the Iowa caucuses, but won their party's nomination and, of course, the subsequent general elections.
What about Mike Huckabee, Dick Gephardt and Tom Harkin? They came in first in Iowa but failed to become their party's standard-bearer.
Iowa has always chosen its presidential candidates using caucuses, but the caucuses didn't achieve the significance currently attributed to them until 1972, when the Democratic Party moved the contest to the beginning of the year.
Since then, however, only three non-incumbent candidates who won Iowa have gone on to win the presidency.
Seven democrats in 10 caucuses who won in Iowa have ended up winning their party's nomination, according to the Des Moines Register. (Two were incumbents who ran unopposed.)
Six Republican winners in Iowa, out of nine contests there, have gone on to win the GOP nomination. (Three were incumbents who ran unopposed.)
So a win in Iowa can give a candidate momentum, but by no means guarantees the party's nomination.
But Bloomberg Businessweek's Greg Giroux adds that the Iowa caucus is also known for ending presidential campaigns, so we may see some campaigns go the way of Hermain Cain's after Wednesday's voting. In fact, since 1972, no candidate who has finished worse than fourth place in Iowa has won the Democratic or Republican nomination.
As of Tuesday evening, polls show Mitt Romney, Ron Paul, and Rick Santorum in a virtual dead heat.
Click here for more about how the Iowa caucuses work.
Click through the slideshow to check out some of the winners of past Iowa caucuses: