By the time Texas has enough registered Hispanic voters to make a political difference, it’s possible that many second-generation Latinos will be assimilated and less reliably Democratic than their parents. Already, researchers are finding that a sizable number of Hispanics later self-identify as white, dampening the trajectory of steady Hispanic growth into the future.

In Arizona, where immigration has played a central role in the state’s politics, racial polarization has become more pronounced during Obama’s presidency. In 2008, with immigration-reform supporter McCain as the GOP nominee, there was only an 18-point gap between his performance among whites (59 percent) and Hispanics (41 percent). In 2010, with McCain touting his border-security bonafides as he ran for reelection to the Senate, that margin grew to 25 points. Meanwhile, Gov. Jan Brewer, who signed one of the most restrictive immigration laws in the country that year, won 61 percent of white voters and just 28 percent of Latinos. By the 2012 presidential election, there was a 41-point gulf between Mitt Romney’s standing with whites and Hispanics.

That year’s Senate race offered a preview of how Democrats can compete in the future. Democrat Richard Carmona came within 3 points of GOP Sen. Jeff Flake, on the heels of overwhelming Hispanic support and running ahead of Obama with white voters. But even that wasn’t enough to prevail, despite Carmona’s unique appeal to both moderate whites and Hispanics as George W. Bush’s surgeon general.