Never before in modern history has a French presidential election been punctuated by so many unforeseen events of all kinds, judicial and electoral.
The April 23 first-round vote ended with a four-way split, ranking centrist Emmanuel Macron first with 24.01 per cent, followed by Marine Le Pen of the Front National (FN) on 21.30 per cent.
Mr Macron and Ms Le Pen are therefore heading for a second round run-off on May 7.
First polls gave a ratio around 60/40 in favour of Mr Macron.
As in recent campaigns in democratic countries, the French public has been deluged with polls of various kinds.
Each shift in voters’ stated intentions is passed under the microscope and commented upon.
While the very reliability of polls has been questioned given the unexpected victories of the Brexit vote in the UK and Donald Trump in the US, pollsters regained legitimacy with their rather precise predictions of the first round result.
The central question is how predictable the final outcome can be based on an extrapolation of the polls.
However, if using probabilities can capture the appreciation of what may happen, in the case of a single event — a presidential election, say — the notion of probability doesn’t actually say anything about what is really going to happen.
The weight of abstention
To make a credible prediction, we need a model that allows us to consider the evolution over time of the different voting intentions and so to predict what they will be on the day of voting.
I have developed a model using what’s called “opinion dynamics” within sociophysics, a growing field of research especially among physicists.
This model allowed me to predict the victory of Mr Trump as early as the summer of 2016.
Applying the model to the French presidential election shows Ms Le Pen is out of reach of victory with an active glass ceiling, which maintains her below 50 per cent of people’s voting intentions.
Nevertheless, beyond the declared voting intentions for the two candidates in the second round of the French election, a phenomenon that’s more difficult to gauge is the abstention rate.
As I shall demonstrate, if people decide not to vote, it could tip the balance in favour of the candidate placed in second place in the polls.
Polls currently suggest the abstention rate in the second round could be the highest ever for a French presidential contest — between 19 per cent and 22 per cent.
In general, abstentions benefit candidates from outside mainstream political parties, but this time both the mainstream right-wing Républicains and left-wing Parti Socialiste were eliminated — Ms Le Pen and Mr Macron are thus both outsiders.
This is why it’s essential to have a general study of two competing candidates in an election and then apply it to a specific case.
I have gone into the details in a scientific article, but the implications can be explained relatively simply.
When Ms Le Pen’s father Jean-Marie, founder of the FN party, unexpectedly made it into the second round of the 2002 presidential election, the country’s other parties formed a “Republican front” — collectively voting against the far-right FN.
In the first round, the leading candidate was Jacques Chirac with just 19.88 per cent, followed by Jean-Marie Le Pen with 16.86 per cent; in the second round, Mr Chirac won with 82.2 per cent over Mr Le Pen’s 17.8 per cent.
That required a large number of voters who’d initially supported other candidates to vote for someone who wasn’t their first choice.
The last day counts
However, the second round of the 2017 election is unique as a large number of voters who do not want the FN to win will have to vote for Mr Macron whose politics they strongly oppose.
Trapped between a repulsion for Ms Le Pen and an aversion for Mr Macron, they will force themselves to make an unpleasant choice and vote against the far-right.
Nevertheless, to implement this choice will require them to cast a ballot for Mr Macron, which for some will be like swallowing a large, bitter pill.
That’s why it’s quite likely that a significant number will take advantage of any “good excuse” at the last moment to not take the time to do so, and so boost the abstention rate.
I define this novel behaviour as an “unconfessed abstention”, which in turn will produce a differentiated abstention at the collective level.
This means we can realistically assume that there will be more abstentions among those who say they will vote for Mr Macron than among Ms Le Pen’s supporters.
On this basis I can calculate the difference between the rates necessary to make up the distance between the two candidates and so reverse the final ranking.
For example, if Mr Macron were polling at 58 per cent and Ms Le Pen at 42 per cent, and 90 per cent of those who say they’ll vote for her actually do so, she would get more than 50 per cent of the vote if the participation for Mr Macron falls below 65.17 per cent.
By definition the unconfessed abstention rate cannot be evaluated by polls, making it more difficult to forecast the final outcome.
This means that in addition to the battle to reach a maximum of voters in the polls, mobilisation on the last day is likely to be decisive.
So, despite the “Republican front” and Ms Le Pen’s polling below 50 per cent, she could still become the next president of France if the differential abstention rates are in her favour — and it wouldn’t take much for that to be the case.
Serge Galam is a physicist and theorist at Sciences Po in Paris.
Originally published on The Conversation
