Sunday's gubernatorial victory for PRI, which ran Mexico for 71 years with a heavy hand before being ousted in 2000, makes it a clear favorite ahead of 2012 presidential polls.
The number of internally displaced people in Mexico pales in comparison to those forced to flee rural areas of Colombia, for example, but the number is growing.
The Mexican government and police efforts in the Mexican drug war are often undermined by the control that organized crime has on the political system.
Three brutal killings in Mexico in the past few days, including today's car wash massacre, killed at least 41 people. Most of the victims were formerly involved with drugs.
A reduction in crop yields caused by climate change could mean up to 6.7 million additional Mexicans will emigrate to the United States by 2080, says a study by Princeton University researchers.