It will be the first time the GOP presidential candidates will get any results from their months of campaigning. And it will set the stage for the future of the candidates' campaigns. It's been a roller-coaster race so far with lots of shuffling in the polls.
If you don't like the polling today, just wait until tomorrow. It seems they keep changing in Iowa -- a place that is still seemingly up for grabs.
The battle for Iowa is not just fought on the ground at stump speeches or small gatherings.
"It'd be a terrible mistake to have a liberal Republican or a moderate Republican stand up against Barack Obama," said Michele Bachmann.
It is played out on the airwaves and on the internet with ads that play to patriotism.
"This election is about more than jus t replacing a president. It's an election to save the soul of America," Mitt Romney says in a political ad.
Our sense of security.
"No one has done more to protect America from Iran's growing threat than Rick Santorum," another political ad says.
A desire for a Washington that works.
"We need a solution. That's the reason I called for a part-time Congress," said Rick Perry in one of his ads.
A better economy.
"We can create millions of jobs right now. My plan includes repealing laws that raise taxes," Newt Gingrich said in a political ad.
Or a message that rarely changes.
"Consistent. Incorruptable. Guided by faith and principle. Ron Paul. The one we've been looking for," said one of Ron Paul's ads.
So much effort and time and money is spent in Iowa because it is the first and because the voters there are different than most.
"They take this very, very seriously and they really put all of the candidates through the ringer. They really try to assess people and it's a big first test," said political consultant Adam Harris with Horizon Strategies.
Harris has experience at every level of campaigning. He says there's something different too about the race this year. SuperpPACs -- third party interest groups -- are running ads for and against candidates, greatly adding to any candidate's spending power.
"It's definitely having an impact. You're seeing a preview of what will come in November," Harris said.
As for November, Iowa is just the first place where we're seeing candidates cannibalize members of their own party, something that could hurt come the general election. Or as Harris sees it, it could help.
"The candidate who does finally emerge as the nominee has been tested. Everything's been gone through. There's no surprises. They are ready for the attacks the opposing party will put on them," he said.
Even though Democrats in Iowa aren't voting on Tuesday, they aren't left out of the equation. President Obama will be hosting a live town hall meeting on the internet for supporters gathered at various locations throughout the Hawkeye State.
Don't forget that we'll have complete coverage of the Iowa caucuses. Eyewitness News reporters Tom Abrahams and Ted Oberg and will be there and will bring you live reports ABC13 Eyewitness News starting Sunday night.