WASHINGTON - A south Texas rancher, Texas sheriffs, an Arizona district attorney and other law enforcement representatives urged Senate committee members Wednesday to heed their warning: The porous southern border of the United States is a national security risk. Witnesses told Sen. John Cornyn, R-Texas, chairman of the Immigration, Border Security and Citizenship subcommittee, at a hearing on border violence that without cooperation from Mexico, combined with federal support from the United States, the situation at the border will continue to deteriorate. Cornyn focused the hearing on recent reports of Mexican military incursions into the United States, increasing border violence...