Mexico's problems with Zetas and Cartel henchmen didn't suddenly appear. They were in gestation ever since the country shook off the oppressive political, economic, and social control of the PRI (Revolutionary Institutional Party) after 70 years of party dictatorship. The change took place in the year 2000 with the election of Vicente Fox, leading member of the opposition party, the PAN (National Action Party), a right wing faction that has always been supported by the private sector and by the Catholic Church. The PRI nevertheless remained one of the strongest political parties thanks to the support by unions and the lower economic level of the population; nothing can be done in Congress without their support.
Felipe Calderon, the current President and also a member of the PAN, decided early in his term (6 years) to confront drug traffickers head-on by deploying the military all over the country. This tragic mistake ignited the present war between all factions involved in the lucrative drug business. Why he didn't strengthen the existing police force instead is every Mexican citizen's acute question. Granted, the population at large trusts the military much more than the local police, but they certainly don't like to feel that they live in occupied territory. Wherever you drive in Mexico you are going to see heavily armed soldiers guarding highways and strategic points in the cities. Instead of making people feel more secure, the uniforms and weapons give the impression that a fight may start at any time. Many unfortunate citizens have been caught in the crossfire! So many innocent victims have fallen under the bullets of both the army and the bandits that common graves are still being uncovered regularly. In spite of the hardships, citizens still go about their business normally and try to shake off their fears. It's all about being at the wrong place at the wrong time.
When the country decided to remove the PRI from power, they also removed the linchpin that held conflicting criminal groups in check. Only the PRI had total control of national security. Every provincial governor owed his (no female governor at that time) position to the central committee located in Mexico city, the capital. Elections were rigged to favor the party in power and important positions were given to selected cronies or even to opposition members to give the appearance of democracy. Needless to say, corruption was a big factor at all levels of government, starting with the then President who was always a member of the PRI. Secret alliances were formed between various sectors of society and there was a mutual understanding that peace benefited everybody. Repression was of course an important tool of the authoritarian government. The infamous Tlatelolco massacre in 1968 revealed the extent of the federal government's fear of a revolution. Hundreds of students and innocent bystanders were massacred by soldiers sent to put out the democratic fire initiated by the new well-educated generation.
In a few words, the strict controls and the special arrangements that were in place during the PRI era disappeared in part with the opening of the democratic process. Yes, corruption is still endemic at all levels of government, but a sincere effort has been made to root out government officials who take bribes from criminal organizations. Ordinary citizens still don't trust their elected officials nor do they trust the various police forces, whether local or federal. However, by making the army the main tool to combat crime, President Calderon has painted himself into a corner: He knows that he cannot win this war and yet has done little to improve local law enforcement (mainly with subsidies). How long will the soldiers remain in position? What will happen when they leave? His quandary is very similar to our situation in Iraq or Afghanistan. The local military and police force are woefully inadequate to protect the population and yet we cannot stay there forever.
The next Mexican President will surely come from the PRI as all polls indicate. The population has concluded that Calderon has made the situation worse, not better than 6 years ago. They hope that by giving the PRI control of the country, relative peace will return and give them a chance of building a better Mexico, though the price to pay may be steep indeed.