Telles and Ortiz are hardly right-wingers. They denounce immigration restrictionists as nativists, and blame the failures of assimilation on racism. But the logic of their analysis -- even if they flinch from the conclusion -- suggests that less immigration would promote assimilation "because opportunities for speaking Spanish, living in barrios, and marrying other persons of Mexican origin would diminish."

They propose a "Marshall Plan" for the public schools. Good luck. As Mark Krikorian points out in his book, "The New Case Against Immigration," pro-immigration conservatives have their own fantasy that the anti-assimilationist ideology of multiculturalism can be rapidly beaten back. Not likely. Here's a more attainable idea: If we have a population of Americans of Mexican origin who are having trouble getting a firm grasp on the rungs of upward mobility, the last thing we should be doing is importing poorly educated Mexicans to further overwhelm their schools, compete for their jobs and populate their neighborhoods with people even less poorly assimilated than they are.

The fate of Mexican-Americans is crucial to the country. In 1970, one out of every 70 children born had a Mexican immigrant mother; today it's one out of 10. No single foreign country has ever accounted for such a large share of births. Astonishingly, more than half of these mothers have not graduated high school.

For a frank discussion of any of this, don't look to John McCain or Barack Obama.