The first-in-the-nation voting contest is rapidly approaching and each candidate is scrambling to either solidify or improve their polling numbers. With just four days to go, the latest poll numbers show Mitt Romney in the lead in Iowa. Ron Paul is polling in a solid second place, and it appears as though the race is on for third place among four other contenders.

Candidates spend a great deal of time and resources in Iowa, but just how important, historically speaking, is a victory in the Hawkeye state?

The Iowa caucus has had about a 50 percent "success" rate when it comes to predicting the nominee, meaning that roughly half the time the winner in Iowa goes on to secure their party's nomination for president. On the Republican side, among the winners of the past six Republican caucuses, three have gone on to win the GOP nomination. George W. Bush, Bob Dole and Gerald Ford each won Iowa, but John McCain, George H.W. Bush and Ronald Reagan did not emerge victorious after that first vote.

Democrats have about the same prediction rate. Since Iowa moved to the first in the nation voting contest in 1972, five out of the total nine Democratic victors in Iowa have gone on to become the Democratic nominee for president. Two of them - Barack Obama and Jimmy Carter - have gone on to become president.

As for that third place finish - the candidate who secures that spot will be in good company. Three former third place finishers have gone on to win their party's nomination, and two have gone on to become President; Bill Clinton placed third in 1992, as did both of the eventual nominees in 1988- George H.W.Bush and former Massachusetts Gov. Michael Dukakis. (Interestingly enough, George H.W. Bush finished first in Iowa when he ran against Ronald Reagan in 1980.)

Even a fourth-place finish does not necessarily indicate that a candidates run is over. In 2008 John McCain finished in fourth place, coming in just behind former Sen. Fred Thompson.

With this historical context in mind, don't expect the GOP presidential hopefuls who do not win in Iowa to immediately throw in the towel. New Hampshire will hold their contest just seven days later, and everything can change in the Granite state.