Unfortunately, there is, Art. IV, Sec. 3 of the US Constitution. Unless you can get Congress to go along. Although there might be a loophole in the language that would allow it, but don't hold your breath on the Courts allowing that loophole, even if people in the to be incorpated areas held a vote.
That secion was violated with the creation of West Virgina out of Virgina,unless Virgina wasn't a state at the time, in which case the Union Army was off conquering a foreign country, not putting down a "rebellion". Of course Lincoln got it both ways, having the Confederate states be in rebellion and yet carving W. Va. out of Va.
Moving the Texas borders would almost by definition mean increasing the percentage of liberals, so just having the not liberals moving to Texas would seem a better idea.
Maybe. OTOH, you might have a better chance of having an "open season" on them in Texas.