On Mexico's congressional election day last week, one enterprising politician hung official-looking posters outside his house, set up a booth inside, got two unsuspecting policemen to stand guard while neighbors lined up to vote. By the time his game was discovered that afternoon, the phony booth contained stacks of ballots that had to be discarded.
Apart from a few such incidents, the election went off calmly. Most of the 2,560,000 voters on the registration rolls went to the polls in the heaviest turnout ever (under a new law, eligible citizens who fail to vote can be fined). For the first...