Killings in Mexico expose cartel power and political vulnerability

In Mexico, a wave of bold political assassinations is putting new pressure on the country's fight against drug cartels. Last week, a mayor in the western state of Michoacan was gunned down during a public celebration. He had openly challenged the cartels. Days earlier, a lime grower who spoke out about extortion was also murdered. The back-to-back killings show how dangerous it remains to oppose organized crime. From Mexico City, The World's Tibisay Zea reports.