Since the November election, in which U.S. President Barack Obama won huge majorities among minority voters, it's been taken as gospel that the Republican Party must, for its own survival, seek to appeal to those groups by moving to the left on topics such as immigration reform. But as the nation becomes more diverse, the demographic shift can cut the other way, too: Some Democratic voters are likely to move to the right.

It's assumed that, as the United States becomes increasingly nonwhite, white Democrats will continue to support the party. But a substantial amount of social-science evidence suggests a different conclusion: As the U.S. becomes more racially and ethnically diverse, liberal whites might start leaning Republican.

Consider a straightforward experiment I conducted last year: Over two weeks, I sent pairs of Latino men in their 20s to ride commuter trains in the greater Boston area, often cited as one of the nation's most liberal regions. These people were not asked to do anything out of the ordinary, just to wait for the train and ride it. The pairs I sent were native Spanish speakers, so when they spoke to each other, it was probably in Spanish.