Under Mexican law, electors living overseas are allowed to vote, but they can only do so if they return home. In effect, this rules out the majority of Mexicans in the United States because it involves a journey that is both prohibitively expensive and - for illegal immigrants - includes a potentially dangerous border crossing.
The lack of a postal vote for expatriates does not appear simply to be a question of logistics. Officials within the Mexican government have reportedly conceded in private that they suspect that emigres tend to vote against the government, which has been controlled by the Institutional Revolutionary Party (PRI) for 65 years.
The issue has prompted Latino organisations in Los Angeles - which has more Mexican residents that any other metropolis in the world except for Mexico City - to stage a 'symbolic ballot' to publicise their plight. They argue that many Mexicans in the US, who send millions of dollars home annually, play an influential role in Mexico, and remain deeply concerned about its politics. No accurate figures exist for the numbers involved, but they are large; there are an estimated 13.5 million Mexicans in the US, although not all are eligible to vote.
From today, Mexicans in southern California will be able to cast token votes in ballot boxes set up in public places. The organisers, led by the Democratic Revolution Party (PRD), one of the two main Mexican opposition parties, will distribute more than 100,000 ballot papers, bearing the names of the nine presidential candidates.
The protesters admit that the outcome of the mock election will be academic, but they hope that it will make their point.