The leftists in Mexico come from the deep south of Mexico, where most of the Indians are who hold an endless grudge against both the Mestizo (half Indian/half Spanish) Hispanics and the White Hispanics and White Americans as opressors. Most from north of Mexico City are fairly "American" in their outlook, as far as that is possible in Mexico.
I think the ones who were living in what is now the USA were most like Americans in their outlook --- they liked the "frontier" away from their big centralist government. You never read much of any riots or protests by them when that former Spanish territory joined the USA. Mexico City is modern in the affluent areas --- but they seem more like Europeans to me than like us.
What I find interesting --- half of the state of Zacatecas is now living in the USA --- but that state just elected a PRD governor --- and we consider the PRD party to be one of the more leftist. Mexico City has a PRD mayor and it's interesting because he very well could be the next president of that country.