There is a two-volume DVD set doing the rounds in Mexico’s capital city at the moment showing the blurred picture of a man in an open-necked white shirt and the words “Who is Mr López?” in big white letters across the bottom.

It is a question that is taking on increasing relevance. As Mexico prepares to elect a new president on Sunday, Mr López, alias Andrés Manuel López Obrador, is slightly ahead of the centre-right Felipe Calderón in most polls and there is a growing feeling that he could win.