All the elements are in place for big trouble in the aftermath of Mexico's disputed presidential election. Manuel López Obrador appears to have lost to conservative Felipe Calderón, but says he'll declare himself the "legitimate" president of a "parallel" government. His claim that the official vote count was fraudulent has been rejected unanimously by the nation's top electoral court. The leftist supporters of the former Mayor of Mexico City already occupy the public venues where the conservative current president, Vicente Fox, plans traditional ceremonies on Friday. Can López Obrador make political life impossible and force another election? If Fox exerts his authority, will there be violence? What's the possible fallout North of the border?