The 2016 Iowa caucuses have all the makings of an historic night for Democrats and Republicans, with a real possibility the current two frontrunners Hillary Clinton and Donald Trump could be beaten in what remains a very close race.

It’s been an election that has in many way re-defined American politics and the way campaigns are run. So when all things are said and done, what are the major storylines you should watch out for tonight as the results are pouring in?

1. High Turnout Bodes Well for Bernie Sanders and Donald Trump

The big question surrounding the Republican race is whether Donald Trump’s supporters will show up to caucus or avoid the process altogether. In a caucus, there’s no absentee ballots or a full business day dedicated to voting, allowing Americans to head to the polls before, during, or after work. You have to physically go to a location at 7 p.m. CT in your neighborhood, even if the temperatures are cold and a snow storm is looming. Caucuses can also last two hours.

With a strong ground game, offices all over the state, and more than 10,000 volunteers, Bernie Sanders can expect to have his support out in force. But where they caucus and if that voting is too concentrated in certain areas is the big question.

The key for both Sanders and Trump is motivating the first-time caucus-goers they’ve been able to bring to their Iowa events to come out in large numbers, similar to what happened in 2008, when turnout doubled.

2. Where Will Romney 2012 Voters Turn? Read more in ABC.