Mexico's missing local election candidates

With general elections coming up in Mexico, the head of the federal electoral body says he does not believe the country's criminal organisations will try to influence the presidential outcome.
However, in local elections, the drug cartel's home turf, some towns are being left without candidates due to threats.
Controlling the municipalities is key for Mexico's drug organisations because the heads of the municipalities are more vulnerable to corruption due to the cartels' influence.
The central government is either unable or unwilling to protect the local districts' candidates.
Al Jazeera's Lucia Newman reports from Monterrey.