The top two candidates go through to a second election and voters choose their favourite
On the first election day, voters mark their preferred candidate with an “X”, if the candidate wins 50 percent of the vote they are elected, otherwise a second ballot is held, usually two or three weeks later.
For the French National Assembly, all candidates winning more than 12.5% of the votes of registered voters, or the top two candidates if two candidates didn’t make it, go through to a second round. In other countries just the top two candidates go through. The candidate who wins the most votes in the second ballot is elected.
The Two-Round System is similar to the Alternative Vote (AV) and Supplementary Vote (SV).
Whilst It is slightly more representative at the constituency level than First Past the Post (FPTP).
It has many of the disadvantages of First Past the Post (FPTP) such as wasted votes
It is often said that in the first-round you vote with your heart, and in the second you vote with your head. Hence there is less need to vote tactically in the first-round.
It is highly disproportional and favours large parties.
Second-round bartering encourages parties to remain friendly with each other (although this tends to be true only within broad party “blocs”).
The voting process is drawn out over a period of two or three weeks and possibly longer.
It is easy for voters to understand and is simple to count.
The first-round encourages a certain amount of tactical voting because of risk of the compromise choice not reaching second-round.
If no compromise candidate reaches the second-round, it can lead to surprising outcomes: Jean-Marie Le Pen of the French National Front qualified for the second-round in the French Presidential election in 2002. This ultimately gave Jacques Chirac one of the biggest electoral landslides in French history.
Excluding smaller parties can foster disillusionment with the political system
When a number of candidates get to the second round, they can agree amongst themselves that one of their number should stand down to exclude a third.