Serge Galam says in this NYT piece that abstention can affect the election in France. He says abstention from the far left voters is likely to favor Marie Le Pen. He says an overall abstention rate of 25% shown in polls can make it possible to have an uncertain result, and that Le Pen may need much less than 50% of the vote if abstentions are high. If 95% of Le Pen voters turn out and less than 61% of Macron voters turn out there is an opening for Le Pen, says Galam.
Another way of looking at this is the disaffection of the electorate with parties in France, with a high abstention vote even if Macron wins, especially on the far left.
Original article 6 minutes, gist 1 minute