This FairVote list says that Texas is not one of the states that binds its electors to vote a certain way. Furthermore, the worst penalty I've heard for "faithless electing" is something akin to Florida's penalty of $1,000 fine, a misdemeanor charge, and disbarment from future electoral colleges. But there's a non-negligible likelihood that any state law interfering with an elector's decision to vote is actually unconstitutional, though I don't believe such laws have ever been challenged.

Not to count unhatched chickens, but what happens in the event of a royal upset December 19th and Trump receives less than 270 votes? Will the entire reselection process occur later that day? As I understand it, there would have to be the Electoral College upset, then the House of Representatives called into session (I don't believe they're in session on 12/19, or any of that week for that matter), the candidates are summoned (do they speak to the House before the vote?), the House vote occurs according to rules of intrastate quorum and majority, then, assuming no tie occurs, the candidate is selected. This doesn't sound like it'll happen in a day.