WITH presidential candidates stumping coast to coast, the national spotlight is once again flashing on three facts politicians can't long ignore: California is the state with the most people, most electoral delegates, and most immigrants.
This year, as Republican hopefuls and President Clinton load up their bags of rhetoric and factoids, a significant new study of immigrant behavior here is debunking long-held myths and providing well-researched answers to some of the state's - and nation's - thorniest questions: Do immigrants, for years after they arrive, remain mired in poverty? Are they unwilling to learn English? Do they separate themselves from the American economic mainstream?
The two-part study, ''The Changing Immigrants of Southern California,'' comes when much of California's highly popular, anti-immigration initiative (Proposition 187) has been struck down by a judge who ruled that only the federal government has the power to restrict immigrants' rights. But now, a spate of federal legislation, working its way through congressional committees, could mandate similar limitations nationwide on legal immigrants' benefits.
Tracing the progress of southern California immigrants during the 1980s, the study concludes that new arrivals are assimilating and improving their economic condition at a fast pace. One of the most comprehensive studies of immigrant assimilation ever conducted in the state where 40 percent of US immigrants reside, the findings could have political implications for policymakers.
''The speed of immigrants' upward mobility is striking,'' says Dowell Myers, professor of Urban and Regional Planning at the University of Southern California. Summing up his study, which analyzes 1980 and '90 census data to examine how immigrants changed over the past two decades, he says: ''The quantitative results are dramatically different from those of more conventional studies or from casual observation.''
One key finding is the growing income levels of male Latino immigrants from 1980 to 1990. When lumped together as they are in conventional studies, their personal income declined by 8 percent during the decade. But by tracking specific age groups and adjusting for inflation, Mr. Myers found Latinos aged 25 to 34 in 1980 saw their average income climb from $14,890 to $18,899 a decade later - a 27 percent rise.
Other surprising results: Among Asians who arrived in 1980, 67 percent had become US citizens by 1990. Some 53 percent of Asians spoke English by '90, and the number in poverty was only 6 percent. Across all ethnicities, when comparing 1970s immigrants with native-born Americans of the same race, upward advancement was generally faster for the immigrants.
Noting that California is just emerging from a devastating recession and the state's mood is decidedly anti-immigrant, Myers says: ''The pace of occupational mobility, increasing income, declining poverty, and business startups all bode well for immigrant participation in the region's incipient economic recovery.''
New research method
The report is winning kudos from immigrant-monitoring groups from California to Washington.
Harry Pachon, director of the Tomas Rivera Center, a nonpartisan research institute, says the study corroborates for the first time what has been hidden in national studies over the past 20 years. ''By following waves of immigrants in a controlled way, Myers is showing the progress Latinos, Asians, and whites make that is lost when the groups are measured as a whole,'' Mr. Pachon says. ''This should help close the gap between reality and rhetoric in this year's political discussions.''
Some praise Myers's methodology but criticize his analysis. ''Myers has done an excellent job compiling statistics, but some of his conclusions do not follow,'' says Ira Mehlman, analyst for the Federation for American Immigration Reform (FAIR). ''He says immigrants are doing well except for those who are not doing well, which turns out to be a pretty large percentage.''
The study measures the progress of groups of foreign-born residents of white, Asian, and Latino origin. Grouped according to age and the date of their arrival in southern California, the immigrants reside in the state's seven southern counties.
Among the other findings:
* Self-employment: Of the groups that were 25- to 35-years-old in the '70s, white immigrants increased their self-employment rate from 15 percent to 35 percent in a decade, Asians from 8 percent to 21 percent, and Latinos from 3 percent to 11 percent.
* Personal income: Both sexes in all ethnicities improved. Among whites and Asians, groups aged 15 to 34 and 25 to 34 doubled their personal income in a decade. The increase for Latino males was more modest, but still 26 percent for ages 25 to 34.
''Politicians and the public tend to paint immigrants at the extremes of wealthy or bottomed out and unskilled,'' says Lucas Guttentag, director of the Immigrant Rights Project of the American Civil Liberties Union. ''This study shows clearly how simplistic that old view is and the extent to which immigrants are trying to embrace their new land.''