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The Iowa caucuses are perhaps the most important yet mysterious contest in American politics. The concept of an election is familiar to everyone – but by its very name, a caucus sounds different and archaic. However, give or take a few wrinkles, the Iowa caucuses are simply another election, held on a cold winter’s night in the Hawkeye State. But those wrinkles do matter quite a bit.

Republican frontrunner Donald Trump and his daughter, Ivanka, try to get out the last-minute vote ahead of tonight’s caucuses. Photograph: Rick Wilking/Reuters

Is it the same process for Democrats and Republicans?

No. Whereas Republicans have a relatively straightforward process, in which they cast secret ballots in their precinct caucuses, it’s far more complex for Democrats.

Republicans

Republicans have a secret ballot. Voters take a piece of paper and mark the name of the candidate whom they support. These votes get counted in each precinct and reported to the state party.

These totals are supposed to be reflected in the final Republican delegation to the national convention. Rules implemented after Ron Paul finished third on caucus night in 2012 but eventually controlled Iowa’s delegation are supposed to enforce this.

The totals reported on caucus night are simply normal vote tallies as in any other election.

That is not the case with Democrats.

Democrats

Democratic caucuses are quite undemocratic. Each precinct is apportioned a number of delegates based on Democratic turnout in the past two elections. It’s like an electoral college at a micro level.

This means turnout doesn’t matter. If a precinct is supposed to have five delegates to the county convention, it doesn’t matter if eight people show up to the Democratic caucus or 800. The precinct is still only getting five delegates. (Precincts elect people to the county convention, which elects people to the district convention, which elects people to the state convention.)

After attendees show up to a Democratic caucus, they are divided into preference groups based on candidates whom they support. Bernie Sanders supporters will stand in one area, Hillary Clinton supporters in another. Once everyone is separated, there is a first count of how many supporters each candidate has.

To be viable in each precinct, a candidate usually needs to receive the support of 15% of those who attend, although in some small rural precincts, the threshold is higher.

If a candidate’s support is under that threshold, his or her supporters need to induce others to join their group in order to reach 15%. If they are unsuccessful in doing so, their candidate is not considered viable and they can either go home or support a candidate who is viable instead. There is then a second count of supporters for each candidate and, from those totals, delegates are assigned.

This means that if Democratic candidates are polling under 15% statewide on caucus night, they could significantly underperform compared to their polling.

Key demographic groups

Despite this socially conservative slant, the key group in Iowa on the Republican side in 2016 will be more moderate “country club” Republicans. With Donald Trump and Ted Cruz appealing to those conservative voters looking for red meat, if moderate Republicans in the eastern part of the state coalesce behind one establishment candidate – Marco Rubio, Jeb Bush or Chris Christie – it could make this a three-person primary, with evangelical, conservative and establishment camps each emerging with a viable contender.

On the Democratic side, students will be the key demographic to watch. This will be the first Iowa caucus in over a decade that has taken place when colleges and universities are in session. If Bernie Sanders can successfully organize and turn out young people across the state, it could give him an edge in several key counties across the state.

Turnout will also be important on the Republican side, as many of the voters most attracted to Trump’s candidacy are new to the political process. The higher the turnout, the better for Trump. In contrast, overall turnout is a mixed indicator for the Democratic primary. While Sanders is also hoping to turn out a number of voters new to the political process, an increase in turnout doesn’t necessarily bode well for him. After all, while Clinton may have lost the state in 2008, she still vastly surpassed her vote goals and likely turned out more people than every other Democratic candidate in the history of the caucuses besides Obama.