It looks like a
weasel or a
mink to me, but I've never seen either of those in the wild before. From your photo, it looks much more like a mink than a weasel. Were you near the Rio Grande River? If so, my vote goes to it being a mink, since minks prefer habitats near permanent surface water. The weasel has more "raccoon-like" facial markings which are not evident in your photo.
Anyone else care to venture a guess?