Michael Penfold (who is critical of Hugo Chávez) has an interesting look at Henrique Capriles Radonski and the Venezuelan opposition in the current issue of Foreign Affairs. Beyond the Venezuelan political context, however, he makes the following point:
Incumbents in Latin America rarely lose reelection bids. In the last three decades, there have been only two: Daniel Ortega in Nicaragua and Hipólito Mejía in the Dominican Republic.
Is this true? Augusto Pinochet lost his referendum to remain president, though it was not a re-election bid because he'd never been elected in the first place. In some countries, like Mexico and democratic Chile, presidents either can only serve one term or must wait one term before running again (thus making it impossible to be an incumbent).
Latin American presidents who might have lost a re-election bid have tended to resign or otherwise leave office (sometimes by force) before facing voters. Or they simply steal the election. Alberto Fujimori did both--he stole an election and then later resigned. The lack of a no-confidence vote means a string of coups, coup attempts, and forced resignations. Overall, it's a pretty depressing statistic.