No matter how many times you run through the Mexican presidential candidate Andr�s Manuel L�pez Obrador's "50 Commitments" � a brief document that serves as his campaign platform � you won't find the following words: "environment," "sustainability," "air quality," "contamination," "pollution," "biodiversity." Nor does his 2004 book "An Alternative Project for the Nation," a more detailed position statement, deal with the environment. It's simply not a subject the candidate chose to raise when he set down his goals. This noteworthy omission doesn't need to imply that L�pez Obrador is weaker on environmental issues than his four opponents. It mostly reminds us that he's the only candidate risking scrutiny by publishing a political platform in the first place. But it also underscores the marginal position that the environment occupies in Mexico's political debate.