The extremely tight race – Calderón won by 0.5% of the vote – and the profound disappointment suffered by López Obrador and his supporters led them to contest the ruling of Mexico’s electoral authorities, and to refuse to acknowledge Calderón’s victory. Instead, López Obrador, a former Mexico City mayor, and his supporters demanded a vote-by-vote recount, which is not mandated – though it is not proscribed – by the country’s electoral laws.