Just a decade ago, Brazil had achieved such success liberalizing its oil and gas sector, an endeavor it launched in 1995, that it had become the gold standard for energy reform. Mexico, on the other hand, was struggling to push through measures that would enable its oil industry to keep growing. But in the ensuing years, the Brazilian government took a sharp turn toward resource nationalism as Mexico City made strides toward liberalizing its own energy sector. And the tables could turn yet again, perhaps as soon as 2018, when Mexico will hold its next presidential election. International oil companies have watched the tides of leftism, nationalism and protectionism ebb and flow in Latin America over the years, and this cycle will continue to play out in the region's leading oil producers....