It is my understanding that only four states published declarations of the cause of secession.
http://members.aol.com/jfepperson/plat.html
All four of them stated that slavery was the reason, including Texas.
http://members.aol.com/jfepperson/reasons.html#Texas
The more northerly states favored the Crittendon Compromise, which would have maintained slavery in the slave-holding states. After the failure of the Crittendon Compromise, the rest of the slave-holding states seceded.