If the action is non-violent in the "we want a divorce" mode met with a Texan resolve of "we're just not going to sit here and obey Washington's dictates any more", I think freedom can be won because then neither the Left nor the Right would support Romney in a military response.
The trick would be to erect border fences (on the states) and print currency so that a secession action can begin establishing itself as a new country from the beginning. If you have borders, money and strong leadership with a plan to execute, the new nation can start operations before DC knows what happened.
I think it can be won without firing a shot. The new nation would have to be willing to negotiate with DC on various federal operations on Texas soil (military bases, etc.) and Texas will have to pay for some of their freedoms but if you explain it like a business that divests one of their assets in order to raise funds to keep the other businesses afloat, a capitalist like Romney can even see some sense for the US to let Texas go their own way.
Simply have Texas' governor announce "effective today, we will no longer obey the orders of Washington DC nor send them our tax revenue. We are forming our own nation with our own Constitution and our own currency. We will begin today to establish sovereign foreign relations with any country that wishes to recognize us and commence doing trade with then. We come in peace and do not wish any form of violent confrontation. No citizen of Texas will be held against their will if they wish to leave but if they do leave, we reserve the right to control our borders and those leaving may not automatically be allowed to return..."
Texas would have the best change of an independent existence. It has oil to back up any currency and a strong sense of cultural and political identity. However, this is likely to be the last election the GOP will win easily in Texas. The advance of Hispanic identity politics casts a pall over that state. Witness Perry stupid remarks on immigration. Also note the type of people who are the mayors of cities such as Dallas and Houston. The liberal rot is spreading within every state with any significant ‘diversity’ population.
Rather odd to think that having 50 states feverishly printing money will lead to greater monetary stability than the federal reserve system we have now. We tried that approach under the Articles of Federation, and it didn’t work.
If you can’t get 3/4s to amend the constitution, you can’t get 3/4s for secession. Anything less would be rebellion, and would be punished harshly.