French citizens in some overseas territories in the Americas and South Pacific were heading to the polls on Saturday to choose the next president, a day earlier than their mainland counterparts. Emmanuel Macron, the centrist incumbent who was first elected president of France in 2017, is facing several challengers but the most formidable is the far-right’s Marine Le Pen. France is the world’s seventh-biggest economy and a main driver of policy in the European Union. A win by Le Pen, a strident eurosceptic who is in favour of tough anti-immigration policies, could upend European politics. Polls…