Democrats and Republicans follow quite a different procedure to select their nominees at the Iowa caucuses.

The process in Democratic caucuses is complicated, more time consuming and according to some analysts, even outdated.

At the caucus site, separate areas are marked for each candidate and participants express their support by standing in the area of the candidates they want to support. Then, for about half an hour, each group tries to convince others to join it and undecided voters could visit each group to seek information about their respective candidates.

At the end of this period, the supporters of each candidate are counted and supporters of those considered not viable are asked to choose another candidate. Thus, second preference sometimes plays a major role.

The threshold for viability of a candidate is between 15 and 25 per cent.

Then some time is given for the campaigning and after that head count is taken to see the support each candidate has received. The caucuses sent delegates to county convention, which in turns sends representatives to district conventions and State convention.

Both district and State conventions decide on the delegates to be sent to the national convention where the nominee is finally chosen.

For Republicans, the procedure is much simpler. Each participant is given a blank page to write the name of the candidate of his or her choice and after listening to campaigning, they cast their votes by secret ballot.

Delegates from precinct caucuses go on to the county convention, which chooses delegates for districts conventions and which in turn selects delegates to the State convention, which ultimately selects the representatives for the National Convention where the nominee is finally chosen.