The poll is asking the wrong question. The right question is whether or not Texas has the right to secede. A good followup question would be whether or not the necessary conditions justifying succession are close to being satisfied.
The U.S. Constitution does not expressly recognize or deny a right of secession. Accordingly, the argument for a right of unilateral secession begins (and pretty much ends) with a claim about the very nature of the Constitution.
That document, by the terms of its Article VII, only obtained legal force through the ratification by nine states, and then only in the states so ratifying it. Because the Constitution derived its initial force from the voluntary act of consent by the sovereign states, secessionists argued, a state could voluntarily and unilaterally withdraw its consent from the Union.
In this view, the Constitution is a kind of multilateral treaty, which derives its legal effect from the consent of the sovereign parties to it. Just as sovereign nations can withdraw from a treaty, so too can the sovereign states withdraw from the Union.