At present, the Texas Nationalist Movement has a petition with 1 million signatures directly calling for a vote of secession.
From Think Progress.
The Civil War established the precedent that a U.S. state may not unilaterally leave the United States. But, as the Canadian Supreme Court recently opined when considering the case of Quebec, the international law norm is that a state or province may leave a country lawfully if suitable political approval is secured from both the state and the country that it is a part of to approve the separation.
If the Congress passed a law, approved by the President, allowing Texas to leave if it had the approval of its voters, and the voters in Texas approved a referendum calling for secession, the split would be legitimate.
Would this be so bad?
In 1861, secession would have meant a continuation of slavery in Texas, which was an agricultural economy with significant reliance on slave labor. Oil would not come to change everything for another four decades.
But, in 2010, would a Republic of Texas be so unconscionably worse than the status quo that a vote of the people of Texas on that issue should be disregarded?
It also wouldn't necessarily lead to the rest of the United States unraveling. The fact that Texas was an independent Republic for four years or so, and was part of the Confederate States of America for another four years or so, has colored how Texans view their own political identity. Texas is an exceptional case. While other states were part of the CSA, had periods of independence (Hawaii, California), or were previously ruled by Spain (Florida, New Mexico, Arizona, California and parts of other states) or France (Louisiana) or Russia (Alaska), none have held on to their prior political identity so proudly.
Ironically, this is a politically opportune moment to allow a vote on secession in Texas.
The departure of Texas from the United States would cripple the Republican party, which is already well on the way to becoming a Southern regional party. And, even if the vote was to remain in the United States, Southern conservatives would have their patriotic credentials and credibility tarnished for generations, harming the party in less restive states.
Democrats, in contrast, have everything to gain politically in the rest of the country from the departure of Texas, which is a Republican stronghold and a major barrier to national consensus on environmental issues, criminal justice issues, and more.
Also, if a bill to allow the vote was signed by a black President, it would also give the crypto-racist supporters of the measure the cover they would need to win a popular vote, making the vote one of patriotic loyalty, as much as anything else.
I don't think that Texas should leave the United States, although it would be a tremendously interesting development to watch, but I am not deeply opposed to the idea in principle either.