What's funny is that there's a theory that's not inherently crazy (except in the sense that's common to all amusing legal theories that will never be tested) that of all the states Texas is the only one that can make a legal claim to being able to secede because it was an independent state annexed by treaty which had specific provisions in it, the theory being that Texas could simply abrogate the treaty. No other state, except possibly Hawai'i, ever had terms like these. I personally think the readmission after the Civil War would supersede this original claim, in other words, Texas could have left then but couldn't come back and leave again. Now all that said, the platform doesn't even try for this theory instead simply declaring it the right for Texas to secede but never outlines why cities and counties can't then secede from Texas. They'd have to rewrite the Texas Constitution first. (Which would be difficult if their platform was passed since it requires three-fourths of counties to endorse any Constitutional change.)