Still, the Macronia has been sounding the war drum for weeks now, claiming that Le Pen might edge a win if not enough voters go to the poll. They also warned against premature complacency, citing the precedents of 2016 in the UK and the US.

Technically, it is possible of course, a low turnout in general except for the Le Pen voters might swing the vote. But the comparison to the 2016 Brexit referendum and the Trump election are misplaced: prior to June 24, most polls were only showing a narrow (3-4%) lead for Remain and at least one poll was predicting Leave. As for the US elections, Clinton actually won the popular vote (like Gore did in 2000); Trump was only elected thanks to the Electoral College.

The cynical me tends to think that the Macronistas are not so much worried by a Le Pen win, as improbable as it may be, but rather by a not so large victory of Macron: this would put a damper on Macron's momentum and perceived "legitimacy" to pursue his agenda. They are also planning for the Legislative elections in two months from now: Macron's election in 2017 carried forward into a large majority for his party, LREM, in the ensuing Legislative elections; a narrower than expected victory today could cast a doubt on pulling a similar majority this year.

Also, a large number of those casting a ballot for Macron today are doing so, not because they are supporting Macro, but rather because they do not want to see an extreme right president in the Elysée (yours truly very much included).