I'm guessing the effect is more Hispanics moving into the area, rather than Hispanics swinging from Romney to Clinton?
Actually, I think it is a mixture of local Latinos that are more established "Old Tejano" residents, that typically would tend to lean Republican, combined with a higher birthrate than the "Old Anglos" and the children and grandkids are coming of voting age, and voting more like Millennials in other parts of the country.
We need to remember that most of these counties are extremely sparsely populated and there isn't a ton of net migration into this region, and as I have stated multiple times rural WestTex was one of the few regions where there was a net swing towards Obama between '08 and '12, and I suspect that with Trump as the Republican nominee it swung even harder Dem this year than before, simply because this dude Trump is not a typical Texas Republican, even among older Tejano voters and there descendents.
I don't know what counties you or Figueira are specifically talking about, but there has been a lot of Hispanic immigration to a lot of the meat packing counties in Kansas. Seward County (Liberal) is now majority Hispanic, and Finney County (Garden City) is inching its way there.
The counties in southwestern Kansas that swung towards Clinton (according to the NYT map) are Seward, Haskell, Finney, Stevens, Grant, Stanton, and Wichita. All of them still voted heavily for Trump, of course.
Thanks for the info.