As Americans head to the polls on November 5, immigration is a key issue on many voters' minds. For migrants trying to reach the United States by land, neighbouring Mexico is the final hurdle of their journey. To keep caravans away from the US border, undocumented migrants are sent back from the north to the south of Mexico. They're forced to stay there until they get an appointment on the "CBP One" application system to formally request asylum in the United States. In the poor state of Tabasco in southern Mexico, these migrants are growing impatient as well as anxious ahead of the US presidential election. Our correspondents Quentin Duval and Laurence Cuvillier report.