Matt Barreto (better known on Slog as the pollster behind the Washington Poll) has a post up on Latino Decisions in which he wonders if pollsters are (once again) missing the Latino vote. For example, two recent national polls showed Obama winning Latino voters by only 48-42 and 53-44 margins respectively. But eight national surveys exclusively of Latino voters show Obama winning an average 70.3 to 21.9 percent of the Latino vote.
Let’s examine how these faulty Latino numbers create problems with the overall national estimates. Afterall, Latinos are estimated to comprise 10% off all voters this year. If Latinos are only leaning to Obama 48-42, that +6 edge among 10% of the electorate only contributes a net 0.6 advantage to Obama (4.8 for Obama to 4.2 for Romney). However, if instead Obama is leading 70.3 to 21.9 that +48.4 edge contributes a net 4.8 advantage to Obama (7.0 to 2.2), hence the national polls may be missing as much as 4 full points in Obama’s national numbers.
[...] This is the exact story of the 2010 Nevada data in which poll after poll showed Angle ahead of Reid, and Latinos only slightly breaking to Reid. On Election Day Reid won by 5 points, an 8-point swing from the poll average, and he carried Latinos 90-to-10.
According Barreto these polling errors come from small Latino sample size, non-representative samples (Barreto says that robotic IVR methods have "notoriously low and problematic response rates among Latinos"), and a failure to interview enough Latinos in Spanish—problems that have plagued pollsters for decades. It's an interesting perspective from an academic who specializes in Latino polling. Read the whole thing.