The issues regarding the Rio Grande Valley remind me of the issues I ran into when making my 2012 White Obama Lovers by County map last year.
With Texas specifically, I had to continue tweaking, and tweaking, and tweaking...and tweaking my formulas to get something that looked believable for most of rural Texas. In most states, a rather uniform formula could be used; where there are Latinos, it doesn't work. With TX in particular, it was even worse. I had to create a whole range of scenarios to balance out everything.
In the northern part of the state, I kept running into issues with white support for Obama being negative - even when bumping down Latino turnout and support for Obama to ungodly levels even by Latino standards. There are still counties on the map where white Obama support is at like 1-2% after all of that, including bumping Latino support for Romney up to 60-70% in some cases.
In South Texas, it was the opposite. White support for Obama kept producing ungodly levels of support that were showing up as majorities in some counties. It doesn't help that white population in some of these counties is so small that moving Latino support by 5-10 points shifted Obama's white support by 50 points. I continued to increase Latino turnout and (mostly) support to levels comparable to black voters in order to get something halfway realistic. Even then, the share of white support on the map still sticks out compared to the rest of the state, lingering between 25-30%.
(It's worth noting that this broader trend - whites seeming to be more in favor of Obama in the more heavily minority rural counties than in neighboring rural counties with smaller minority populations - was something I ran into to varying degrees quite consistently throughout the country, including in heavily Black and Latino areas, the former of which is much easier to project in terms of turnout/support)
Anyway...I'm wondering if there might have been some truth/accuracy to my initial projections for the map, in that whites were actually unusually Democratic in these heavily Latino counties and that - when combined with drop-offs (potentially? haven't looked yet) in Latino turnout in these areas - a huge swing among the otherwise small white vote to Trump there was enough to swing the Rio Grande overall to Trump, even though Latinos may have been more Democratic this time around and/or turned out in larger numbers? It's worth noting again though that in many of these Rio Grande counties, I had Obama at 90% among Latinos...so I'm not sure how they could have gotten much more Democratic there than they were in 2012.
And maybe that's why there's a swing to Trump there: they didn't, but the whites swung to Trump by a very large amount and Latino turnout (at least in raw numbers) was either down or there wasn't enough of an increase to cancel out white swing. I do have a hard time believing Trump improved among Latinos overall, whether in TX or nationally.
I'm guessing Whites living with a bunch of Mexicans are going to be comfortable with them and vote for a president that understands them and appreciates their presence.
Also how did Obama get some White votes in OK and AR? Huh?
