Lascuráin was the foreign minister in Francisco I. Madero's cabinet. On 18 February 1913, General Victoriano Huerta overthrew President Madero. To give the coup d'état an appearance of legality, Huerta had Lascuráin assume the presidency; Lascuráin then appointed Huerta to be his interior minister and promptly resigned, thus handing the office of president over to Huerta.
Lascuráin was thus president for less than one hour (sources quote figures ranging from 25 to 55 minutes). Huerta subsequently offered him a post in his cabinet, but Lascuráin declined.
Lascuráin received a law degree in 1880. He served as mayor of Mexico City prior to being selected for his cabinet position on 10 April 1913. He was the director of the Escuela Libre de Derecho, Mexico City's top law school, for 16 years, and he published extensively on commercial and civil law.