Step inside an office building in the town of Nanterre, just west of Paris, and you are confronted by what the nostrils register as an odor of the past, for it’s a rare thing these days to encounter the lingering taint of cigarette smoke in public spaces. The trail of it leads upstairs to a corner office and to the woman who has, in the past few months, come to dominate French newspapers and chat shows, where she is depicted variously as the new face of European bigotry or a herald of a new European political realignment.