Murder of Arizona rancher puts spotlight back on illegal immigration

The recent murder of a longtime rancher has rekindled the debate over illegal immigration in Arizona.

Robert Krentz was found shot to death on his property near Douglas, Ariz., last Saturday. U.S. Border Patrol agents tracked footprints from the crime scene to the nearby Mexican border. Some have speculated that Krentz was killed by an illegal immigrant, but no arrests have yet been made.

Former Rep. Tom Tancredo (R-Colo.) used the incident as opportunity to blast Sen. John McCain (R-Ariz.) and Homeland Security Secretary Janet Napolitano. "Each one of them is culpable in this man's death," Tancredo told FoxNews.com.

McCain reacted forcefully to the news -- reiterating his call for troops to be deployed to the border. "I am asking you and the Administration to immediately reconsider your position and send National Guard troops to our southern border region," he wrote in a letter to Napolitano on Monday.

But the crime -- and the reaction it's sparked -- is a reminder that McCain remains exposed on the controversial issue.

His primary opponent, former Rep. J.D. Hayworth, remained critical of the senator.

"One of the reasons [J.D. Hayworth] is challenging John McCain, is because of McCain's past sponsorship of legislation that would grant amnesty to illegal aliens," the former congressman's campaign said in a release expressing condolences to the Krentz family.