With less than two months before the first round of the French presidential election, immigration is once again a major campaign issue for a number of candidates. While the issue has always been a source of passion and tension, "the debate has become more radical," says François Héran, chair of Migrations and Societies at the Collège de France, and author of the book 'Parlons immigration en 30 questions' ('Let's talk about immigration in 30 questions').