COLUMBUS, N.M. – This dusty little border town with almost no visible means of support has been seeing something of a boom in the past year: Brand-new Lincoln Navigators and Cadillac Escalades with flashy wheel rims are parked just off the bleak main drag. Homes are selling quickly, sometimes for cash. The source of this sudden wealth? An influx of Mexican drug smugglers, investigators say. The smugglers are fleeing the Mexican army's occupation of the town of Palomas, on the other side of the U.S.-Mexico border fence, and settling in Columbus, where there has been a law enforcement vacuum. The...